Okay, so it's not much. He's only having a few bites of kibble at a time. But it's better than before, and he's acting totally normal--scrambling around into the window or onto Mom's record player so he can peer outside, following me around and yelling at me, all that. So I'm hopeful.
Yesterday Mom took him to the vet and got prescribed a people-antihistamine which apparently encourages appetite in cats. So far, it seems to be working. We're not out of the woods yet, but things are looking better. One of the vets we took him to thinks it was some kind of random allergic reaction--we'll have to figure out what it is he's allergic to. o_o But we'll do our best.
So thank you, everyone who offered suggestions or wished my kitty well ♥