Thanks for all the tips, everyone. I’m trying a new food to see what he takes to. I did find Fancy Feast at the store, but the varieties I can find all have types of grain gluten listed as the fourth ingredients, though broth and meat (beef / turkey, etc) are the first through third ingredients and they do show added taurine on the label. I’ll probably have to do a run to the pet store and see what I can find there.
I had been feeding him Sheba’s ‘Premium Cuts’ type of food, which basically looked and smelled exactly like chicken. When I switched to that food, it was because his bowel movements smelled absolutely awful with the previous food, and they were much better after I switched to the Sheba stuff. I’ve been trying to research on the internet, though, but it’s really hard, because any food I look up has various complaints about it from SOMEBODY. I’ve seen people claim that what I feed him now is not actually intended to be food, it’s supposed to be a treat only, even though it says ‘food’ on it and it has directions for being fed as a nutritionally complete diet, or this person’s or that person’s cat wouldn’t touch it, et cetera.
Plus Sheba has decided to discontinue the type of food I feed him, because of ‘economic reasons’, they’re stating on their website. I pay about 90 cents/can, which seems to be cheap for that brand considering what I’ve read on the internet (some people were paying almost 1.50/can), but the other types some people have suggested as better actually seem to be even less expensive.
I’ve purposely tried to avoid the cheap ‘filler’ types of wet food. If I’m specifically feeding him wet stuff, I definitely don’t want to give him filler. That defeats the whole point 
I will definitely be checking with the vet too (I have an appointment for two weeks from Monday), since I seem to be feeding him about the same amount and types of food as my sister feeds her cats, and they’re quite lean while mine is very chubby. I think hers actually eat a bit more, because they graze on their dry food all day between wet food feedings, though I can’t let mine do that, or he’ll gorge and get sick. So, obviously his individual needs are different.
Thanks again for all the tips, I really appreciate them. I’m sure we’ll find something that works, I want him to be a healthy, happy kitty.