if you are going to feed only canned then you need to be brushing his teeth every day or every other day. also give him dental chews (not rawhides there's a difference.) his tummy is upset and he is vomitting because of the sudden change in foods, i think the gradual change was explained in another post.... have you tried adding a little dry in with the ceasar's? if you get a dry food such as royal canin mini puppy the pieces are soooo tiny he wouldn't have a problem with chewing those pieces plus he will be getting his ceasar's which he loves so much and the crunchy benefits of the dry food will be there as well as the great quality and dose of beneficial nutrients. but if you are going to do this, do it slowly, add a few pieces of food to his food he gets already. you dont' want to keep upsetting his tummy but you do want him eating nutrionally sound foods.