You may want to start a separate thread in the health forum. There should be a "post new thread" or similar button at the top of that sub forum when you go there. I'd check the size of the feeders you are using. You should be giving him a prey item that is about his width at his widest point. Rat fuzzy would probably be adequate at that size. And yes, a 5 day schedule should be fine.
If you do post a new thread, they will want to know if he is pooping / urinating correctly, what your temps are (low, high, etc.) and humidity levels too. If you are not having any other weird symptoms, then he probably just needs to be bumped up to a slightly larger feeder size.
My local petsmart typically gets very small BPs...maybe ones that have eaten
3-4 times if that, so he could have been very young when they got him.