What about a bed in the walk-in attic? And his clothes in tubs instead of your fabric in tubs? If the door remains open most of the time, would it stay warm enough for him to sleep in it? The former bedroom is now your room - don't make him too comfy or he won't have the needed incentive to find a way to be on his own again. IMHO the room should stay as your craft room. Good luck with whatever you decide.