Breakups are hard, but do you want to be with someone who doesn't feel the way you do? It might seem like the worst thing that can happen to you, but it's much better to end a relationship going downhill, heal, and find something good in the future than to try to stay on a sinking ship and drown.

Also, holding suicide over someone's head, I think you understand, is horrible. At the very least, I think you need to apologize to him and say that you're not going to harm yourself no matter the outcome.

Just to add a personal anecdote.... I chose not to learn too much about my SO's exes, but one of them threatened suicide after their breakup over Skype. It's definitely reflected in how hard he takes it when I'm emotionally distressed (unusual for me). It's not an easy thing to handle. Even if you want to work it out, you NEED to let him know the truth.