Your dog had MAJOR abdominal surgery. If you, as a human had this surgery you probably would not be given solid food for 2 weeks, and you would still be in the hospital. His stomach will be painful, and he will experience nausea for several weeks.
Dogs can be partially fasted for awhile with out problems as long as they drink water. I would allow him small frequent bowls of chicken soup, meat broth, or fish broth with a small amount of rice or noodles for a few more days than slowly add canned dog food seperately, but, only 2 tablespoons per feeding every 3 hours. A probiotic, either as a supplement, or in yogurt or cottage cheese can also be used in addition to the canned dog food. Don't add dry dog food for 2 or 3 weeks. If your dog is still having problems maybe your vet can add an anti-emetic (anti-vomiting/anti-nausea) medication.