I liked this movie
To answer your questions:
1) No he wasn't in a coma, he suffers blackouts.
2) Kayleigh did die in one reality, however he changed that and went into a new reality/timestream where she didn't.
3) He did lose use of his arms until he was able to change realities/timestreams again.
4) Well it all goes back to the point of the movie. He was a mistake. He never should have existed and as such he finally corrected things in the end.