Thanks, Dee!
Personally, I think I'd want to cut back on how much you give him in each meal, just to see how he does and because there is such a thing as being too acidic. Maybe instead of 1/2 dropper, go to 1/4 dropper. If you're not comfortable cutting the dose that much, maybe just reduce it to a bit less than 1/2 dropper and see how he handles that. If he's ok, keep it at that dose for a couple of days and reduce it a bit more, etc. It could be that getting it 3x/day is what helped him, and not so much the amount of the ACV, but I could be wrong. Or it could be pulling the Wellness did the trick.
For the record, and I think you already know this, we're sort of in uncharted territory here. I haven't found anything about using ACV to increase stomach acidity or improve digestion in cats (other than the article Dee posted, which is bit more general), which is what we're (hopefully) doing. So I am going on what I've learned, what my gut (no pun intended) tells me, and what you report. Every cat is different and input from everyone else is more than welcome, as I'm by no means an expert.
Dee commented in the other thread on ACV that she would split the dose listed in her post between the meals. I would agree.
BTW, how many meals does he get each day, and how much food in each meal? Finally (I hope), how much does he weigh?
P.S. I just realized -- he's willingly eating food with 1/2 dropper of ACV in it? Wow!