@Aprilcherry04 I know you are pissed off and worried, but the more you post, the more I am beginning to feel sorry for your tenants if you're this stressy and angsty and precious with them!
FGS don't refuse to renew their contract, just tell them that they should really have asked first, and write a new clause into their NEW contract regarding the cats. As for the TV wall bracket holes; big deal, that can be fixed.
I think sometimes, some landlords and landladies forget that their tenants are actually human, with personalities, and hobbies and interests, and actual LIVES. Live and let live; you chose to rent your property out, you're going to have to give a little bit, and not just take the rent off them, and moan when they do something painfully trivial!
Also, why does it matter if you have a cat allergy, when it's not you living at that particular property? 
Seriously, let it go. Cats are the best, most chilled out pets in the world, and will really cause no damage at all to your property. Stop worrying.