Idea #1: No, don't. Linux isn't anywhere it needs to be to be fun. Most games that'll you want won't be supported unless untiler much later after release if at all.
Idea #2: I guess you could do that. I don't understand why you want to just play a game, then shutdown your computer, and then start it back up to boot into linux.
SLI is good now.
I don't know about Gysnc for linux
My reason for having Ubuntu GNOME:
I work on making scripts and web applications which Linux is need for. (Python is shit on windows. Most packages for it are only on linux)