1. Best to ask them via email exactly what you want to know and what documents they may want. I've asked them and they always replied.
2. Yes, 2000 in bonuses that you clear just like rakeback. There used to be more bonuses that are better for micro stakes players, just read up what they offer at this moment.
3. The rakeback % depends on your "Fish Buffet" level. I believe it's anywhere from 10% - 50%. The extra bad thing that makes it difficult to calculate your own rakeback is what they call "PVI - Player Value Index". If you are good, your PVI will be something like 0.4 - 0.5, meaning you get half the rakeback points that I fish would get. So that basically cuts your rakeback in half or even more.
4. You cannot use live HUDs, but there is a basic HUD inside the software for everybody. The Sharkscope site is allowed of course, especially if you plan to stake or get staked for some tournaments. The sharkscope HUD is not allowed.
You can download your hand histories and import them in HM3 when you are away from the tables.