Sometimes I like thinking about big theories and then sometimes I feel like the writers are just making it up as they go along and keep changing the rules and the backstory to fit the current story (the last Ben flashback seemed a bit continuity suspect but I wont go into it because Tomtrek will shout at me.)
All set up for the next episode, but surely since we see people in 2007 we know the H bomb didn't go off in 1977.