Howler

Steam needs to install the game in its own file system to work properly, so yes you should let Steam install it.  You can copy over your UserData folder from your original install to its new location in steam and that should get all your scenarios (that aren't stock) and saves into the Steam install.*  Not sure on the exact path for Steam, but all Steam games are normally in Steam\steamapps\common.
*If you have your mods in the "Mods" folder under UserData, this does not appear to currently be read in the Steam install.  You would need to create a "Z" folder under "Data" instead and put all mods there.  Because that was the "old way" with Combat Mission, you may already have your mods there in your original install.  You should also copy over the hotkeys.txt file from UserData to Data as I've heard some people reporting problems with hotkeys on their Steam installs.

A little user made app called "Who's Turn is it?" does an awesome job of managing your PBEM games. It's as easy as pie with that app. 

The quality of the Steam forums depends on the game. Usually wargames have decent communities.

My personal pref would be to lock down the Steam forum to exclusively announcments and direct all users over here.

It's being edited atm, it will be posted to the below podcast in the next week or two.
 
Developer Dialogue (Interview Podcast)
Apple Podcasts: https://podcasts.apple.com/us/podcast/developer-dialogue/id1524192396
Spotify: https://open.spotify.com/show/33DiH9pCrcV9bVw4WeDWmS
Google Podcasts: https://www.google.com/podcasts?feed=aHR0cHM6Ly93d3cuc3ByZWFrZXIuY29tL3Nob3cvNDUwNTYyMi9lcGlzb2Rlcy9mZWVk

As a retired Light Infantry Platoon Sergeant and Sniper with 28 years of service to include several combat tours, this has got to be one of the more interesting threads I've read on a gaming site in eons. There have been some great points made by several people, and it has been very interesting to read all the differing views and opinions, as well as the shared ones. I also have enjoyed how it all relates to CM. Great stuff!
Some general points of consideration regarding combat and firefights that I would like to make in relation to this topic:
1) Most times in a firefight, there is so much noise that it's very hard to hear near misses. You might know you are being shot at by dirt and debris being chipped at you by near misses, but many times you won't hear it due to the multiple, loud weapons being fired, Soldiers and Leaders shouting out orders, and information on the enemy. It's chaotic and loud.
2) As far as U.S. Infantry training goes, when enemy fire is received, the SOP is to take cover and return fire. Almost always 'take cover' means fall prone, and then seek to improve your 'cover' position. For example, you are prone and returning fire, but there is a nice fat tree five feet to your left that would make better cover. You do what you can to move to it, usually by crawling. 
3) Usually, when a firefight starts, there is an initial round of firing, people hit the dirt, and then people start yelling. For the trained U.S. Infantry, that means enemy identification. As an example, it might sound like this "Contact 1100, 3oo meters, squad size". The direction is important obviously, as it alerts the formation to the general direction of contact as well as the distance. The element size is purely an initial estimate to give leaders an idea what they are up against. Of course this whole contact statement gets echoed back down the formation so that teams and squads at the back of the formation know whats going on. Also, it gets refined as the firefight goes on. As you can see, this equals lots and lots of yelling. Add in to that calls for medics, special weapons teams to deploy, new enemy sightings on the flanks or, Heaven forbid, in the rear, and one can quickly see how chaotic it can get. And then there are all the weapons firing and explosions. Like I said, chaos. 
4) Now, all that said, the mark of an experienced and/or well trained unit will handle that chaos much better. That is why SOP's are tantamount to success. When bullets start flying, Warfighters have to react without thinking, for best success. LOTS of time is spent training and practicing on initial contact with the enemy. It is the basic building block for all other Infantry training and operations. How your unit reacts to initial contact can make or break your unit.
5) I must absolutely agree with those above that said you shoot what you can see, and you suppress what you cannot see but suspect might be there. Also, as a trained and experienced sniper, I will always be of the mindset that well placed, accurate single shots are more effective at taking a target out then suppressive fire. But, suppressive fire has it's place. When an Infantry platoon is conducting a standard platoon attack on an objective, and you are in the Assault Element, you definitely want that suppressive fire to be hosing the objective before your assault begins, and then following in front of you as you assault across the obj. When the enemy is keeping their heads down from the barrage of M240 and M249 fire as well as some 40mm grenade fire mixed in, a trained designated marksman or sniper can more easily pick off specific targets on the obj, especially as the assault element is moving across. When all this is executed by an experienced unit, it is a thing of beauty. 
 
Anyhow, some general thoughts. I could talk about this topic for hours and days, but hopefully I've made some salient points. 
 
Cheers!

Biggest thing for me was the infantry behavior fix. It wasn't that they were retreating too much that bothered me, it's that they were retreating into the enemy's fire. 

To be fair, most want to move quickly to contact and then spend the remainder of their gaming session in contact. It's a game. There's only so much mucking about one can do in a 45 minute engagement. Again, it's a game and, within this context - it rewards battle drills over gamey actions exploiting engine limitations. For the most part.

Lots of things can prevent CM from running correctly,  I think you've focused too much on security features. If SmartScreen was preventing the game from running it would prompt you about it with a large popup.
 
A couple years ago I discovered that the Asus Realtek control software prevented CM from running unless CM was launched through a 3rd party shell like Steam, which is weird as ****, but whatever. Try disabling every application in your system tray that isn't critical for your system's operation and launching CM. If it works, then use the process of elimination to track down what it could be. 
 
Also, AVG sucks. I highly recommend going back to Windows Defender. It does all you need without the extra bull**** that will cause more problems.

Thank you that is very kind. Yes, it works with all CM2 games. I purposely built it so you point to your installed game and it makes an attempt to figure out the needed directories but you can override them. That way if BFC changes something you are in control.
I have a new version coming with a few new features. I'm bogged down with real life work and some changes that are causing me grief. I will update people when there is news.

I just wanted to give a shout out to the developer(s) of the "Who's Turn is It?" PBEM Manager.  It really works great for handling your PBEM games automagically.  It is free and works with the free version of Dropbox.  Removes all the hassle from PBEM.  I am pretty sure it will work on all the Combat Mission games.  Thanks @IanL!
or
https://www.lesliesoftware.com/products/WhoseTurnIsIt/

I like Hapless :
https://www.youtube.com/channel/UC9egpHJiRis89uHkeyJiEug

MOUT operations in CMx2 titles have always been pretty bloody if not executed without exceptional care. I can not make a statement regarding your specific situation, but what i ve observed in the couple of years playing CMx2 is that clearing a building occupied by hostile forces is
Best avoided if possible If avoiding clearing the building is impossible, destroy the building or its occupants using heavy fire power (tanks, aircraft artillery, what ever you' ve got). If destroying the building or it's occupants using heavy fire power is not possible, prepare it for infantry clearing by first spending a couple of turns suppressing it's occupants using at least a 3:1 force ratio and the target or target light command. RPGs and the like are wonderful tools for convincing an enemy in a building to leave it. After preparing the building for assault, keep suppressing it with a target-light command and a 2:1 force ratio an send a 1:1 force ratio troop into the building, carefully. Use the pause command and suppress each room with the assault element using target-briefly for at least 10 seconds before entering (this also leads to some grenade throwing, etc). If possible, send the assault element into the building using demo charges by blowing in a wall that has no windows and from the top most floor possible (because hand grenades work best if thrown from an upper to a lower floor). If heavy resistance is encountered in a room, retreat and try to destroy or at least suppress the enemy using your over-watch element from the outside. Using above listed steps, MOUT against an inferior force as the Syrians in CMSF2 can usually be done relative casualty free. Fighting an equal enemy such as the Russians in CMBS, on the other hand, will always cause you some losses, there is no way around it. Just accept it and keep pushing forward towards your mission objectives.

In your documents folder there should be a text file called "display size.txt". If not create a blank text document. There should be three 0's by default. This will tell the game to use the desktop resolution. Alter the first two numbers for the display size you prefer and the third number is your monitor refresh rate.

While the choice is totally yours, there would be no reason to keep the demo when you own the full version.

People were just trying to help ...
Assumptions are always dangerous which is possibly why you are confused but surprisingly you now want to make two without censure.

@ErwinThe tree(s) you see on the screen aren't a true representation and will differ even more depending on mod used. It's best to assume a tree trunk can/will be obstructive any/everywhere in the action spot.
 

No, no, and no! I don't want my gunners to randomly  hit around center of mass. It's hard enough scoring a KO against a Tiger without throwing this into the mix. The randomness you are advocating for already exists in the game when you are actually playing rather than running tests on a target range which is what you all have been observing.
My vehicles blow-up real good as is for all sorts of hits. A main gun getting knocked out is not common for me. Therefore, the very same must also apply to everyone else. No?
 

Some mortars such as the British 51mm team assigned to an infantry platoon are not able to fire indirectly. I don't know if that is the case with the German LMT in your screen shot but assume it is. In any event, when a piece isn't in your support tab - it may only be used in a direct fire role. This requires LOS to the target rather than being in contact with a commander. While mortars are able to target spots on the map that other weapons can't - it's not going to allow targeting of a position that is entirely out of LOS. It will allow a (limited) reverse slope target to be fired on.
You can avoid hitting your own position by using a Forward Observer who is trained to guide artillery and also by not calling missions closer than 600m (aka danger close) from friendly positions.
The big difference between on-map and off-map support pieces that populate the support tab is that the former are able to be used in a direct fire role. Other than that - both will need a line of communication to whomever is calling the mission. Without a TRP (Target Reference Point), your effectiveness will be determined by the quality of the shot caller. With a TRP - the shot caller isn't as critical as the ranging has already been worked out.

Below is a thread discussing buddy aid that may be interesting.  Many questions were asked, discussed and answered in the thread.
 
 
 
The below was copied from the above linked thread:
WIA (red base) can turn to KIA (brown base) from additional hits.
Buddy Aid is one on one however a team can treat multiple casualties in the same A/S concurrently.
A team administering Buddy Aid will recover ammo including ammo for weapons they do not have in the team.
Buddy aid on KIA (brown base) was about 15 - 35 seconds. On WIA (red base) about 1 minute – 2 minutes 30 seconds.
Casualties only disappear if they receive Buddy Aid. I tested 2 KIA & 2 WIA for 1½ hours game time. They never disappeared.
Experience of the teams administering buddy aid did not affect the length of buddy aid or the amount of equipment recovered.
Lightly wounded (yellow base) are not counted as casualties on the AAR screen.
To share ammo recovered in buddy aid the medic team must be part of the unit (“highlighted” unit) needing the ammo.
During testing on average about 2 grenades and 170 rounds of ammo were recovered per casualty. I know from playing the game other                                equipment (radios, binoculars, some weapons etc.) can also be recovered but I did not try for that in the experiments.
WIA (red base) incapacitated wounded are not counted in Parameter/Condition but are counted in Parameter/Casualties.
Buddy aid does not make a difference to the score in Quick Battles or in Scenarios.
Buddy aid does not make a difference to the score in a Campaign.
Buddy aid may only make a difference as a tie breaker in a CM tournament . 
A little disappointed that Buddy Aid has no affect on the score. 
Buddy Aid will keep a WIA from becoming a KIA.  However both KIA and WIA are counted as casualties so the score does not change.  The AAR screen will count KIA and WIA separately but they are both counted as casualties for scoring purposes.  
Below is a method you can use to encourage your troops to administer Buddy Aid I learned this from @IanL  
If the casualty is not in or near the center of the action spot give the unit to perform buddy aid a Slow order to an action square that takes them directly over the casualty. Then I give them a pause of 20s, 30s or 45s depending on how far away the casualty is. Push the BRB. In the next command phase they will be directly over the casualty.  Then cancel the remaining Slow order and issue a Face command.

Hi folks,
I've now made a second beta compilation. Anyone else interested in testing can PM me for a link. I should be on course to get the first proper release into your respective sweaty hands by next weekend. Then I can add a few extras as I make them - crops spring to mind.
I did a quick test of the existing mod in CMFI and CMRT (demo). I could see straightaway that FI will need a lot of work to adapt the mod to it. There are many more very different terrains used so that'll be some time coming. RT is an easier ask, I don't have the full game yet (waiting for a bundle with FR - hopefully 🙏). The mod worked quite well in the demo and added nicely to the overall look of the battlefield. Then there are the Low Countries, autumn and winter versions to come up with - anyone!?
In the meantime ... there's something in the long grass ...
LS

There are some hotkeys which you can look up in game and also in the manual, some of them:
Alt-Z .............................................. Toggle Command Links
Alt-M ............................................. Toggle War Movie Mode
Alt-L .............................................. Toggle Show Landmarks
Alt-J .............................................. Toggle Show Objectives
Alt-I .............................................. Toggle Floating Icons
 
There is no built in screenshot utility, and you cannot hide the game controls at the bottom, but you can cut it from the picture later with your favorite editor.

I believe once the mission enters the 'Firing' phase then the FO can be used to call another mission.

Can't tell from that screenshot.
You'd have to show the comms between the groups in the UI. I can't tell who or what they are or what comms set-up they have.
Also is there any EW setting actioned?

You may want to reach out to @Haplessto ask how he incorporated his TOE snapshots that he uses in some of his videos.
When I first saw them, I thought that would be handy to visualize organizations - then ran into the issues you and others have encountered.😞

This is actually my preferred choice for MP battles, but it is really missing the ability to rewind the action, as you can in SP. I would be so glad if that ability would be added!!