yes, i try not to drop below 55%. 65-70% i believe is ideal. you could try sphagnum moss: dampen a handful and place it in the enclosure or in the hot hide. it works great during sheds!
i don't use heat lamps so allow others to help you here.
changing the hides will stress them out a bit and make them feel uneasy; give her some time to adjust. sitting on top of the hides is a definite sign of stress: "a hiding ball is a happy ball." i'd say monitor her enclosure, temps and all, and try to pin-point a stress issue. feel free to post pictures and ask questions.
there's a user here (can't remember who) whose signature says something like: "ball pythons are consistent in their inconsistency." they require time to "dial in" so to speak, and get just right. like i said before, you are well on your way to helping her. you asking questions on the forum is already a sign of commitment. you're doing fine! can't wait for pics!