My evil twin would be tempted to go to his place, break a bunch of stuff, and then claim you were 'helping'.
Given the depth of his problem - he comes over when you're not there, and trashes stuff under the guise of repairs. You take away his key, so he brings over his own lawn equipment and trashes the lawn. He fails to see either that his 'help' isn't wanted, or that he is actually destroying stuff rather than fixing it.
He's not going to get hints. I'd say it's time for a major freak-out. Get so mad that he can't fail to notice you are upset. Tell him point blank that every time he does this, it costs you massive amounts of time and money. Present him with a bill for the clean up for the last mess he made. Tell him point blank that he's not allowed to do anything in your home or on your property without your written consent *and* personal presence while he does it, and he's not allowed on your property without you there. If he disobeys this, he will not be allowed on your property at all.
Then stomp off in a huff and don't speak to him for a couple of weeks and ignore his phone calls.
If he *does* ignore you, and trashes something else, you send him a bill, and ignore him for a longer period. You also install a simple but noisy alarm system on your back lawn and windows (leave room for the mailman). If you're on good terms with your neighbours, ask them to phone you immediately if they see your father on your property without you.
It sounds drastic, but by what you've described, he's deliberately and willfully done damage to your home that has cost you massive amounts of money to fix. Either you're going to have to get really tough and take a hard line, or you're going to have to learn to live with it, and budget "cleaning up after Dad" money as part of your monthly budget. Or move to an apartment with security.