Before I go spend an hour killing every soul in Riverwood, in lieu of restarting. Is riverwood supposed to become hostile after returning from the claw quest thing?

bug probably

You may have killed a chicken?
Try staying away from that town for at least an in-game week and see if they returm to peaceful.
Ive read about someone whos had a similar problem, and that fixed it for him.

You probably killed someone you shouldn't have.

LOL!! idk if you saw the footage or not. Some guy named "Mangg" uploaded his playthrough a few days ago. While in Riverwood he came to a personal dilemma to kill this chicken in the middle of town or leave it. He literally sat there for about 10 seconds describing the potential pros and cons of this decision. He finally said "screw it" and killed the chicken. The people of Riverwood then drove him outta town for quite a ways. It was one of the most funny things I've seen from Skyrim so far

alot of bugs and broken content so far.

Mangg's particular case wasn't a bug. The chicken belonged to someone, thus it was a crime. He didn't know how to yield properly so he ran away. The OP's issue sounds like a bug fore sure. There is at least one other person reporting the same thing.

>implying you can even yield in this game

I had that problem. Couple people told me to wait 3 days in the game. I waited just over 3 went back to Riverwood and everyone was back to normal.