love Dumeril's boas, he looks nice congrats!
As said previously, if came from pet store would avoid the mulch/wood chips for the first month... just to be safe.
As for the patchy sheds.. that will come with your choice of substate aswell, if hes dragging his belly on that it scratches and dirt will get under scales preventing a good clean shed and making it irritated and red like you said.sometimes other than that humidity plays a good role.
Eating prob..well for starters he looks big enough to be on rats... and what do you mean by feeding live mice in a paper bag? anyways if you can switch to fresh killed or frozen thaw. if hes not eating he may be not used to new home yet like said before give time. He may be used to the same food and it being live. temps also play a big role in feeding response too . hope this helps
and my opinion Dumms have the nicest patterns! good choice over a burm
Ryan