I can help with a few of these...

1)I believe so, from other posts I read.
2)If you were more specific, someone may be able to tell you.
3)Don't think so.
4)There has been so work in this area; perhaps someone else can help you.
5)I know we can add new units, I don't know about more countries.
6)Which file are you referring to?
7)Yes. Multiple ships appear in a stack like grouped ground units.