I think he gets it. What’s not to get about “I need you to leave me alone”? He’s not letting go because he doesn’t want to let go. I don’t think it matters how you ask him–nicely, rudely, cursing him out–he’s not going anywhere.
You don’t explain the details of your breakup or why he won’t let go, but it’s irrelevant. If you truly want to be isolated from him, you have to do it yourself. You have to get tough and cut him off. Ignore his attempts at communication. If they persist, block his e-mail, his text number, his IP address, whatever. Change your phone numbers if necessary. Do what you must.
I know it seems cruel, but he is refusing to give you something that you’ve requested repeatedly. You’ve been patient. Now you have to be tough and take care of your own mental health. He won’t like it, but he shouldn’t be surprised by it. I don’t know what effect this might have on your future friendship, but that’s not important right now. Do what you have to do today to get the peace you need.
Thanks for the question.