Hi Customer (name blocked for privacy),
Has Davidson (I am out on a limb, but...) been neutered? I ask because they get into much more trouble if not.
Drooling, very tender mouth, won't drink... I will bet on a broken tooth, or a cavity that just finally became 'active', or an abscess acquired in his travels. (the creamy part of the drool may be from the infection)
If a tooth, he will likely get to the point where he can tolerate this, as time tends to eliminate the pain in animals. Whether or not you can wait that long is another thing.
An abscess, is best treated with antibiotics and externally by whatever is required. They usually take a few days to become a big bother, so this may have happened days ago.
He may appreciate a trip to the vet. And now would be a good time to fix that 'little problem' if not already done. He could have work done on both ends, and maybe they would counteract each other?
Don't try anything for pain, all the home things are toxic to cats.
Try to go to the vet tomorrow, even first of the week. He may feel better even tomorrow, without professional attention, as draining an abscess improves things, somewhat.
I wish both of you well. If more questions, please ask.
Please check just one ACCEPT box. Feedback is nice, too. Medicine comes in doses of Science, Art, and Miracle, given as needed.