I'm assuming, of course, that you don't owe your employer anything, such as unreturned property or company files. His behavior sheds ample light on what probably motivated you to quit. More than three requests for an exit interview is more than "reminding" someone. It's verbal harassment in my book.
Don't be tempted to sink down to his level with raising your voice and other heavy handed behavior. He does not control you anymore, and it's driving him crazy.
You don't owe him an explanation for choosing another employer. You don't owe him any further communication now that you're gone. You can SPAM the email address and screen calls. You can report him to higher management via a certified written letter stating that the contact is unwanted and that you're hereby requesting that the company immediately cease and desist (i.e., stop it now).
If the harassment persists, contact a lawyer regarding a cease and desist letter or the police regarding harassment. Keep a copy of all emails and a log of his phone calls in case you need them. You don't have to put up with his behavior. I bet you're glad you're gone!