[cypher]

Can you get any paper based substrate like kaytee clean & cosy or even carefresh would probably be better than wood shavings, either that or try putting a good thick layer of shredded toilet tissue over all the substrate.
Does he pee where he sleeps by any chance? A bald patch like that can result from urine burn sometimes although it's not uncommon for older hams to just lose hair there.
You could try adding some extra flax seeds (linseed) to his diet, a little pinch each day which can really help with skin & coat condition, also some evening primrose oil can help, just a drop a day on food.