Just give him TWO. That's all. 2. Then see what happens. If he throws up, next day just give him ONE. See if that works.

Some pets can be like little children, they see a sweet treat and gobble gobble gobble, until they've overeaten and it is too much for the tummy.

My calico Crystal is like this. She gets 2. Not 3, TWO! LOL

Let us know how it goes!