I swear I saw a thread on here where people had the same trouble with the gas issue but it had something to do with the pumps there in Cali. I've never had any trouble what so ever with mine at any of the pumps here in KY.
As far as the reverse thing goes sounds to me like you might be trying to hard to stick the shifter in gear. I've found with both my M6 camaros and the trans am that these cars will easily pop right into gear for you with just a gentle push. If you get to forceful you start missing the right gears. Maybe just pay attention to how you shift and see if that is the cause.
Also havent tested it on the 5th gen yet but the 4th gens had reverse lockout but it only works when the car is moving a certain amount. If the car isnt moving enough its not gonna lock you out. Im guessing the 5th gen is probably the same. If I wasnt laid up with a swollen knee I'd go out and test that theory for you.