Don't apologize for being a worried momma, s'OK. We haven't really tried to determine the vomiting other than to suppose something rattling around in his stomach. If he is just vomiting after you put something down his throat, the addition of whatever it is is nauseating to him. If he tends to keep liquids down, then make sure whatever is in his formula is equally liquid.
Cats are designed by Mother Nature to eat several small meals a day... they can't bold a large meal and expect it to last more than two days without causing some problems. We feel it necessary to get something down a sick cat more often than every other day. Kittens are even more demanding, as are all weanlings. So, with that combination, hypoglycemia is a possibility as a complicating factor.
To help counter that, let's add a couple drops of Karo syrup onto his tongue and see what effect that has. It should perk him up. Try it yet tonight, followed by some liquid formula. Hopefully he will accept it eagerly.
Let me know how he acts Sunday, and Happy Mothers' Day !
Please check just one ACCEPT box. Feedback is nice, too. Medicine comes in doses of Science, Art, and Miracle, given as needed.