you say your dog runs off when you show him his food. Have you had the dog from a pup or is he a rescue dog? Is it play when he runs off or is it fear? please let me know
He could just be looking for attention. Try to make sure he has no access to cat food, put his own food down and walk away. Dogs can be hugely manipulative!
i think you should try a different dog food maybe he tried that dog food and it tastes bad so he doesn't want to eat it anymore so that is what i suggest!@!!