Boy they sure do figure out how to get you wrapped around their little paw very quickly
Sounds like he's a junk food lover. My GP is the same way. I mix a little canned into his dry and he eats it, but put it down dry and he won't eat.
Have you tried a little of the old food mixed in with the new food? He probably threw up the moist food because he ate too much or too fast. You could try giving him just a little mixed or with a small amount of canned food mixed in. Might help get him wanting to eat again. Also how many treats are you giving him? Sometimes we forget how small they are and don't realize how big the treats are too. Please, keep us posted on how he's doing.