That does sound like a tooth issues. Some other signs are dropping the food from their mouth while eating, tilting the head way over to one side while eating, excessive drooling, as you saw pawing at the mouth.
Bubba just about always went off his feed while he had a tooth issues. One issue wasn't even a full year after a cleaning and an extraction! sigh...
You might want to pick up some all meat baby food to give him if he goes off his feed, that would usually keep Bubba eating along with sprinkling a little flortiflora ontop.
I would call the vet and tell them that he is not eating for you and what you observed this morning with the pawing at his face. Once, my practive was going to make Bubba wait about 3 weeks and I was the squeaky wheel about him being a diabetic cat, not eating, and with giving him insulin, not a good thing, yatta yatta. You have an even better plead with a DKA kitty. Tell them that neither of you want to see that happen again and for them PLEASE to prioritize him. And maybe they should cover him with an AB to subdue any infection. That in itself with keep the infection quiet AND he might need something for pain like buprenorphine , but you are all ready giving him that.