You could try something like shredded cardboard animal bedding they don't try to ingest that, he'd then be on a loose bedding, and you wouldn't be worrying about him ingesting the soil/sand and coco pete. Just an idea for you to think over. But I agree the fleece is not helping especially if he's ingesting it.
I also think if its possible is to find a another vet to look him over and see what they say, for a second opinion. They may find something the current one hasnt.