Yah best to join
http://airtreker.com/ - all the answers are already there.
1) FC is high yah, depends on how you drive tho and how you tune/mod your car. For city driving I usually get around 320km per tank. But mine is fairly heavily modified, some members report over 400km regularly and some get 500+ for highway driving (keep boost below 0.3).
2) Ok, normal for turbo engine, 4G63T is an old engine so half cut parts are pretty easy to find. Plus it's basically same engine in Evo 7 so lots of after-market parts too.
3) Yes as above.
4) GB is ok, just take care of it, change the ATF at proper interval (every 15,000km) and don't put full torque down during 1st and 2nd gear, only 3rd gear can really tahan. Turbo of course will have problem sometimes, cos it's mechanical part it'll wear out. It's normal TD04 tho so easily can get repair kit and do full service at Tong Turbo (I just did mine, including full service, some port mod and extending the fins for less than RM1k).
5) Most common problems for ATR is cracked manifold, stepper motor (idle control) and air flow sensor, the rest is pretty solid.
I love my car, no regrets :)