Itās all trial and error, maybe itās pork that he is sensitive to, if he liked the big country raw Kangaroo and duck dinner, then I would put him back on that if he did well with that.
Donāt give up!!
I have done so much trial and error with the dogs food, a lot of people have and itās not something you should give up on, at least you know next time to not buy a big 25lb box of something he has never had before, and to buy the 4 pound bag of it to se did he likes it and does ok with the protein, if you want to try the goat, try the small bag to see how he does with it.
Once you find what works best for him, it will be worth it, you have seen the fur grow back and his cyst disappear from him being on raw, donāt give up