I don't have the map editor (it's windows-only and many users are on Linux/Mac,) but you CAN make maps "by hand." In a nutshell, you make a black-and-white .png image as a heightmap for the terrain, then get a .png terrain image to layer over it, then make an rgb .png with red, green, and blue representing different detail textures for close up. Then you make a .scenario file tying them all together, and adding objects like trees, rocks, water, etc. It's complicated but very fun. There's a great guide around here... http://www.battlefront.com/community/showthread.php?t=78165
As to your next 3 questions, 152's basically got it nailed.
About dropping "anywhere"- You can, technically drop a unit in any location on the map. The problem is that AA is long-range, easy to deploy, and brutal. It's almost never a good idea to drop in an area covered by AA. This makes it possible, using units like the Bacchus or AA towers, to make large swathes of the map "undeployable." This does limit where you can drop, and becomes an integral part of the game. If you take out AA, it's easy to advance quickly by dropping.
Hope this helps, and if you start going online with the full version soon, let us know!