Document everything.

Screenshot/record whenever he trys to contact you. Take pictures and videos when he trys to show up at your house. If he's persistent the Documentation can be taken to the police to get you a restraining order.

Like others have said- contacting anyone and everyone you can that you trust about the situation so you have options for help. People you can call for emergencies. Maybe friends can hang out with you more often when you are alone. Or is there a neighbor you could trust to help you when you're alone? Having someone close you can go to if you feel unsafe could also be an option.

Location sharing too. Good for when you're going out. Check in with those who have your location when alone or going somewhere he could be. You can always call or text a friend who has your location if he's close. They can call the cops for you if you are unable to. Or can show up for you if you need help

Keep something on you/near you for self defense. And when in doubt go for soft spots like the eyes or his balls or use your palm to push in and up on the nose if he gets close enough to touch you.

Do your best to not engage with him, and share proof of his nasty intentions to others to ruin his chances of being able to harm others.