Reply to each thing as something to be happy about.
Half a mouse - Aww, he's brought you a snack, he's so sweet! 💕/ He's such a clever boy, getting rid of the mice for you! What a star!🌟
Bottle cap left off - Oh, thank you for reminding me we need to get some more. As you're not at work, can you pick it up from Tesco's this afternoon?
Washing up in the sink - That was a lovely meal, wasn't it? Can you do something like a simple lasagne, salad, garlic bread and fruit salad tonight? You're such a good cook! 😍
Pile of cat puke on the carpet - 'Poor Fluffy - he needs some homemade chicken broth and a cuddle in the furry throw. It's really easy to make, you just need to go to Tesco's and pick up a tray of chicken thighs, then poach them, strip the meat off, then simmer the bones in water for three hours, then add the bits of chicken back in once you've shredded them by hand, it won't take long/ I'm looking forward to my kitty cuddles tonight after you've done his soup 🐱 '.
Use as many emojis as is necessary to irritate him beyond the point of sanity. Relentlessly, chirpily positive and happy. He'll really hate that.
And then relentlessly, chirpily make yourself an appointment with a solicitor to get the miserable fucker out of you and your lovely cat's lives.