You really need to get a couple more opinions. His immune system is greatly compromised and is why he isn't healing properly. Surgery now would be very dangerous. You really need to put him back on real food and give him good vitamins. I don't know how much your dog weighs, but dogs as small as 2 pounds have had liver shunt surgery and done just fine. Call this office and let them direct you to the best surgeon in your area.
MSPCA-Angell: Surgery Homepage