Sorry if this has been answered before but, if I enter the divide at LV1 to get some things, but leave again to carry on the main game and level up, will the divide adjust it's level to mine when I eventually return to it?

Yes, I believe if you wait long enough (A few in game days), the cells/areas you entered will reset, and then the enemies will have re-scaled properly.

Thanks, Iriodus. That's good to hear. I wanted to clear the hopeville missile silo area early then leave for a while.