I don't think I remember them mentioning going back a set number of hours. It is something to ponder about. But I do get about the final copter scene. Since he already lost the ability, being splattered with the Omega's blood might have supercharged him with it. Might even give him more control of the time loop ability.
You know it would have been more awesome if Rita was wielding a bigass axe instead of that sword like paddle. I have to be honest, I felt that sword paddle was a wee bit small compared to the axe. An axe so huge that you need momentum to be able to wield it properly. And would have made them a lot cooler if they made mention about releasing the autobalancers to be able to wield the axe. My opinion on the metal jacket still stands. The movie version is so fugly.