My guy is 16-17 and lost weight. Fortunately he doesn’t mind the vet or travel and I took him in. He was fine just being elderly. But he’s not underweight so vet not worried about it, and ruled out a ton of stuff.

We give him Vaseline once a day for hairballs. Have an ice cream stick and just put a dab on the stick and he licks it off.

Cats like people can suddenly become sensitive to pollinate he might have had allergies and that’s why the watering eyes cleared up.

You seem to be doing everything you can for him.