1. No. It will create a LOT of copy right problems. You will have to download ST,Babylon5, etc races from this board.
2. Moo3 does not exist yet, so SE IV is infinitely better
I'll buy Moo3 when it comes out but I have a strong feeling I would still play SEIV even then because of its incompariable customisibility.
3. Playing against humans is of course better, but sometimes TDM races at highest settings will give you some masochistic enjoyment