Crazy asshole. So sorry you ran into one.
I want you to take a deep breath. His whole plan is built around scaring you into doing what he wants, and the pressure is designed to take away your ability to think through things and come up with a proper solution.
Are you in an area with a functioning legal system, and do you have evidence of the blackmail? I don't want to pry into what the blackmail is, but I assume it is nothing that would get you in criminal trouble. As a US attorney I'll tell you a competent lawyer around here could get you a solid protective order and hit him with a hard enough threat that he would back off. I understand that you are in debt, so hiring a private attorney may not be an option, but there may be some programs in your area to help with abuse victims (which is what you are. Your "boyfriend" is threatening you. It's abuse. He's an abuser.) Someone at your local courthouse may be able to push you in the right direction.
Don't let an awful person force you to ctb. Ctb is a personal choice you should make for yourself. He deserves hell for trying to do this to you.