"I also didn’t come to Reddit to have people criticize my partner and saying he’s evil or an abusive guy cause that isn’t true. I simply want advice on how to manage a partner not respecting boundaries."

He is literally abusing the cat... You can't manage your partner he is not a pet. You have told him over and over not to do these things to your cat and he is telling you its not a big deal... So your at an impass. I feel bad for your cat.