Can I correct a previous mistake in Fallout 4?

I'm 120+ hours into Fallout 4 and need to know if I can go back to a very early save and 'un-murder' the settlers at Abernathy farm and then return to where I'm now without losing my progress, and for the family to be alive again. I'm new to the Fallout franchise and didn't realize then that it was a mistake. I'm terrified of losing all the time and effort I've put in. Or would it be better to leave them dead, as I don't know whether it affects any thereafter quests? I am playing on Xbox One.