it might help to put a packing blanket over top of jingle bells cage to help keep heat in, if you do make sure you leave space open for fresh air to come in to the cage.
are they bigger than the average size? I breed Netherland dwarfs also and my buck is 3 pounds and I have assumed that he is a false dwarf and have had no peanuts. Hope this helps
He might want a nice place to sit, I have a rabbit that wouldn't use his litter box and just sat in it but once I gave him a box to sit in with a blanket he used his litter box (with a few exceptions):)