P.S. If you can find jars or cans of baby food at the supermarket, you could use those, let down with a little water, for his syringe feeding. Please make sure the baby foods are those WITHOUT onion! And many canned dog foods (or prescription diet canned foods) can be mashed/put into a blender with a little water, for syringe feeding.
I am sorry I have no experience of Epakitin or its possible side effects.
But poor boy -he has been through so much in such a short time! He is probably somewhat shocked by all the surgeries, plus his dog attack. I am so sorry for him right now.
But you are doing the right thing, it seems, and what you are doing sounds good. He is also not getting dehydrated which is positive.
Does he keep the food down? Or vomit? If he keeps it down, then that's a good sign.
It is possible that the Epakitin may taste strange, or have side effects I don't know anything about, due to my lack of experience with this drug -(did you say this is "two scoops" (powder?) with food?) It may taste odd, and put him off his food....
Are the sites of the tooth extractions fully healed? Check in his mouth, if you can, for any signs of ulceration or things not right where the teeth were extracted. If he has pain in his mouth, he will not want to eat.