Hi Lisa,
Chewy can survive on canned food alone. It’s far better for him than kibble is also. Kibble cleaning the teeth is a myth anyway. The best way to clean his teeth is with a toothbrush or by feeding raw, meaty bones or recreational bones.
I have a dog with some food intolerance issues and a bit of a sensitive stomach. He occasionally vomits bile when his tummy gets very empty. It sounds like your pup has the same problem. You could try adding a teaspoon of apple cider vinegar, diluted 50/50 at a minimum to his food. ACV stimulates the production of hydrochloric acid and tells the spinchter at the bottom of the esophagus to close so the bile stays put.
You could also try three small meals per day or, if that’s not practical, give him a small snack a couple times per day to avoid his belly being empty for too long.
Oh, and if he has trouble with transition. Do it slowly. Only increase the amount of the new food and decrease the old when his stool is firm. A spoonful of plain, canned pumpkin will help regulate intestinal water and add bulk to the stool. It usually helps very quickly, and most dogs seem to really like it.
