Sounds like you're doing everything right ( but taking the towel off and on multiple times a day while he's getting adjusted isn't the best idea.). Just bump up the warm spot to 90 and don't let there be a crowd next time you feed him. Try feeding him at night time. And wait about 4 or 5 days before waiting again.
Also, pay attention to the "yawning"... make note if you see him doing it often, or increasingly.
Good luck and let us know how he's doing!
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