I'm a little worried that hay alone won't meet his nutritional needs. I feed Alffy pellets and lots of Timothy hay. Do you measure his pellets to see if he's eating any at all?
It's still hard for me to make out what it is.If it's just a substance I'd try unscented baby wipes to clean it off.If it's a wound you might try some blue kote,I'd clean it first though with a little sterile saline.Be careful not to get it in the nose.
80 degees is way to hot for a chin you need AC. Keep in mind that anything you put in your chins cage they will chew. Even if he's acting OK today I would call my vet to see if he needs any blood testing done. You should also see about finding an emergency vet as most problems happen at night. I hope he's OK.