Gollevainen, I really admire Your imagination and an effort You've made to create all the backstory for this AU!
That said, I must also admit that - as a historian - I just don't consider this scenario (it's history) plausible at all. Of course, this is YOUR AU, so essentially if You say that "this and that happened in that manner" then it has to be so.
My biggest reservations are about the extent of Finland's expansion into Siberia and Far East. I mean, having Finland up to Ob river and perhaps a third state, more along the lines of (real-life) Far Eastern Republic in all the areas east of Ob river would be (in my humble opinion) more reasonable, given the geography, historical and economical procesess etc.
But of course it's Your AU, Your fun (in the first place), and of course it's already too late to change anything major in it, so let's just continue this very interesting thread.