oh, and in the spirit of What Ifs, the answer to all those questions is "they all die."
no, not really.
kong would confront peter, but be friendly and try to help him as spider-man. however, he ends up getting killed, so peter dumps mj and is more sullen than ever.
hulk kills hawkeye, then proceeds to again attack the ultimates. with jan far away, hulk proceeds to decimate the ultimates, crippling tony, killing fury, all before a skrull ship destroys the hulk (and Phoenix, though the remaining ultimates escape via tony's teleportation). the ultimates break up, despite still saving the world.
the ultimates did nothing, really, until the big alien attack. however, in this time, the hulk had been working on the hulk serum, and made it like a serum which had a timed, kind of controlled hulk effect. hulk is unleashed upon the aliens, and the day is saved, and the hulk, but more importantly bruce banner, is considered a hero by all.
ok i'm bored.
Bass, do the rest.