Also something interesting to note.

Sawyer raided his old house in dharmaville and found the ring that HE put there in 1977 so that would mean that whatever happened, did happen and that the bomb going off truly did split the timelines. So his life with Juliet did still occur back in 1977. One timeline where the bomb went off and one where it simply didn't and all the Losties die (which would be the main timeline we are watching).