Okay, so that's a pretty long post, and I'm sure there are more qualified people than myself to answer your questions, but I may as well give it a shot with what I know. 
[hr] [quote]1. (Signup thread, interest checks, blah)[/quote] 
The way you describe is pretty much how roleplays work here. Even in Casual and Free, it's expected for you to make a basic Interest Check in the respective section to find players and introduce them to the core concepts and themes of your roleplay. As for whether you should have the "RP Thread" up right away, it is usually the case that GM's wait for there to be at least some semblance of interest before posting it, however it wouldn't be terribly strange to just have the main thread up right off the bat. 

A lengthy interest checking process does help flesh out and further develop player's interest though, so I would think that it is advantageous.

[quote]2. Activity for "Advanced" ????[/quote]
I'm not qualified to answer this. If somebody who's more active in Advanced could pitch in here, that would be fabulous.

[quote]3. Heat Death of the Roleplaying universe.[/quote]
This literally happens everywhere. The whims of random people on the internet are hard to predict, but I'd like to think that we at least try to not let things die.

[quote]4. Can I spend a lot of my time as a GM going AWOL?[/quote]
From my experience, this sort of varies based on the current roleplaying climate and cast composition. There are a lot of players here that can just go off and start giant, awesome storylines, with little to no GM influence. Usually, as long as you can be active a few times a week, things should be fine~!

[quote]5. Are you people okay with me making a giant badass GMPC?[/quote]
I'm sure nobody will complain if you make a reasonably interesting character of your own, so long as they don't leave a bad taste in everybody's mouth.

[quote]6. Telekinesis is completely overpowered and I hate it. Is this prejudice cool?[/quote]
Yes. Screw Espers, am I right guys?

[quote]7. Can I be hitler.[/quote]
Sure. You can pretty much be as tyrannical as you want in your roleplays, so long as you don't break the site rules. If you're wondering what our level of tolerance for tyranny is here, well, that's mostly up to just how much of a jerk you're being. On a general scale, I would say that as a GM, most people probably wouldn't disagree with your decisions to re-balance or offer fundamental changes to characters you deem "Unacceptable". 

And since you asked, yes, character reviews are considered commonplace on here, at least in the parts of the site I frequent.
[hr]
Alright, now that the Tatsua Question-answering Hour[sup]tm[/sup] is finished, let me just say: Welcome to the site! I sincerely hope you find what you're looking for here, and that we can potentially share some sort of written adventure together in the future!

#Canada