How can Oga be separated from baby Beel? In the most recent chapters (Ch. 232), Oga is finally completely separated from Beel. I do recall minor incidents in the past where they were separated as well, but in the very beginning, Oga would get shocked if he was a too far of a distance away from Beel.

When did this change and what allowed them to separate?
I think it depend on Baby Beel maturity. As long as Beel world's is wider, The Range become larger either. In Baby Driver Chapter, It extended to 15 meter and 8 centimeter and more.