1 - It should fit a GF3 *and* a GF4 through a separate hold-down mechanim. A simple metal plate would do the trick.
2 - I don't know really without any picture. What i can say is, use either 45° barbs or have them stick out quite high above the bottom (like Aquacomputer Twinplex), this because of RAM sinks clearance problems.
3 - It's a GF2 GTS, it produces lots of heat. I don't have any useful figure though, apart from it needs active cooling, and badly.
(side note: if by "at least some" you mean the 6000+ hits on your other thread, then my GF2 produces "at least some" heat
)