The 1st thing is the X58 chipset that all 9XX i7s run on is you need 3 sticks of RAM. As for the other questions
1 Yes, I think 2000MHz RAM is not supported as a stock setting on anything
2 As with any system set the speed in the Bios (instructions should be with the Mobo)
3 not really as with any multiplier locked system increase the frequency in small increments and increase the voltage if it becomes unstable. Keep stess testing to check stability and stop increasing anything when the voltage or temps are 2 high. (this is an over simplified guide)
4 looks very high end I am not familiar with the case or cooler.