"Not a vet, but my mom was a vet tech for years and I've been an animal profession for awhile now.

Cats DO NOT do things because they are mad at you. Your cat did not poop on your boyfriend's pillow as revenge for being yelled at, and they certainly did not pee on your clothes because they're mad you didn't feed them on time. Cats are creatures of habit and prefer routine to feel safe, so when you have drastic changes in behavior (such as eliminating outside the box), it's typically due to one of two reasons: environmental changes or a medical issues. If you cannot think of anything in your home environment that's changed, then you need to get them checked at the vet.

Neither milk nor tuna from a can are good treats for you cat, despite the stereotype.

Unless it's for a legitimate medical reason, declawing cats is cruel. If you don't want cats clawing your furniture, but can't be bothered to do the bare minimum of just researching how you can prevent it, then don't get a cat. Don't have a completely unnecessary medical procedure done on your cat simply because you don't want to be inconvenienced."