What do Seal Point Blue Lynx like to eat?

I am looking after a cat and dog whose owner is away. Theodore, the cat, is said to like dry dog food, but this can't be good for him. He won't eat dry cat food. I've tried. He eats plenty of packaged treats, but that's about it. I bought him a fancy tin of cat food just for an experiment. Theodore ate it like there was no tomorrow. I don't want to change his system. Am I doing the right thing or is this breed vulnerable to drastic change in diet that you know of? ... and quite frankly, should he be eating dog kibble?