Was going to cancel the visit because he improved a lot but I took him in anyway because it was scheduled. Felt a little silly, but I'm new to FIV! They did some baseline blood work instead because he had never had any before.
I have been giving him lysine powder every day for the past week. Maybe that has an effect idk. The vet said I can just give that to him forever if I want and it shouldn't hurt anything.
Verdict is that he will likely always have one watery eye, possibly due to a mild anatomic abnormal. And he might have very mild allergies or very mild asthma which does not really affect his life too much.
But I guess he needs to lose 1-2 pounds so we'll work on that next! He also has some tartar buildup so I'll have to see if I can get him to use dental chews.
So when I got him from the shelter, they told me to give him half a can in the morning, half a can at night, and then "a little bit of dry food" (unspecified amount) as a snack.
You ought to be able to get a vet to give you a good estimate on kcal content if you ask em to.