How do you deal with pesky ex's?
Quit adding to the inventory.
Ignore them, restraining orders seem to work too.
I think you should just tell them to get out of your life....
He is now "ex", why bother! Put an "in" in your life!
Say, "This isn't algebra! Just 'cause you're my "x" doesn't mean I'm your "y"!"
End all contact. Block the number. Have a lawyer send him/her a registered letter advising further contact will be in the hands of the police. Ask friends and family to not talk to you about the ex. Be systematic and consistent. Good luck.
Completely ignore the person. Don't answer any calls or texts. They are looking for you to react ... When you stop they will too.