Some quest I did early on where some bartender was screwing some other guy's wife ended up with one of them dead (I can't even remember which), but sometime later I was approach by a female NPC asking who killed him, and apparently I gave the wrong answer because the whole town started attacking.. I just got away. But are they always going to be that way? Should I re-load an earlier save?

There must a several ways to end that quest. I ended it completely differently.

I'd try just resting 24 hours first as another settlement or something, then come back to see if they still attack. If they do you may need to reload to prior to that woman talking to you.