You have all my problematic cats rolled into one. My chronic vomiters, Angel & Leo, eat the urinary track prescription food because my Maine Coon, Reo, has to eat that, and he is VERY resorceful when it comes to finding and eating foods NOT on his diet. (What brand of kibble are you using? I use...
I also have two chronic vomiters. I was just going over different food options today, and I am considering Blue Buffalo Basics. It comes in both dry & wet formulas, and has very "basic" ingredients, no corn, meat byproducts soy or wheat. I will post back next week and let you know how it goes.