Could he really commit suicide?

I suspect he cares for himself way too much to kill himself. Don't you? Why are you taking these calls? Call the cops next time he threatens suicide. Maybe he'll be stupid enough to tell them the same thing, and the'll put him on a 72 hour hold in the mental hospital for an evaluation. He won't do that more than once. He's just trying to manipulate you, and it's working. Stop talking to him.