Years ago I came across a puppy formula in the AKC handbook. It was five parts evaporated milk and one part water. I would feed him that. If he won't eat puppy food, get some all meat baby food. I have nursed dogs and puppies back to health by putting baby food, or any food, on my finger and putting it in their mouths. Even though they refuse to eat on their own they may swallow the food I put in their mouth.
I bought some puppy milk from petsmart to get me through the weekend. I also have a red heat lamp that I put in the kennel. I'm trying to keep him away from the other dogs incase it is something serious. Thank you for replying so quickly