Well you clearly had made your point clear. It is clear to me that Finland situation was different than another countries in the war. These points you made have been discussed since the war ended, most of them in my point of the view are political questions.
I tried to point out what he did with his divisions in the front against russia. Not what in generally happened in war. After -39 surprise attack by the russians there were only Germany which offered material support. Even finnish army got 100 planes from the US. In summer -40 the situation was "Conquer or to be conquered". In finns in my mind there wouldn't be a possibility to remain as neutral territory since the fear from russian or germany occupation. Worst case scenario would have been that both parties have fought each another in finlands territory.
Also what I didn't point out that Mannerheim tried to hide the finnish army goals so that war in Finlands front would not get too much attention since russians would have deployed more troops there earlier and which eventually would have lead collaption of whole finnish front much earlier.
In the summer -44 there where nothing else do to than drive Germans out of the country since it was agreed so in peace treaty. Only reason why to sign this treaty was not to have Finland occupied which never happened as it did for the rest of the axis forces. Finns mainly fought their own battles for own reasons not because they liked nazi idealogy, mainly because they did see opportunity to strike back and reclaim the land which was taken during Winter War.
Well as you said not good politician, but much more effient in the battles. Became president of Finland only to get finns out of the war. Since russians trusted him so much that if Mannerheim would be behind peace treaty finns surely would stop fighting.
But if you want to write more about this I would gladly discuss this via email