Definitely know the feeling of wanting to show a new pet off haha! If the mice are just under his girth then he could do with sizing up, a little bit wider is fine too. It's surprising how quickly they can out grow prey size, more so as youngsters. The humidity should be bumped up to around 60/70% at shedding time and you could also provide a damp hide, I like to use sphagnum moss in one of them. I bath mine too, while I don't think royals are natural swimmers mine seem to just chill in one, plus who doesn't like a clean ball pythonjust be sure that the bath water isn't hot, just a little warmer than room temperature/luke warm.