Just as King Canute could not stop the tide coming in, neither can you stop him drinking, suiciding, losing his job, or whatever.
Holding you as his emotional scapegoat, hostage is not done from love, but from his need to hang on to someone, for his own purposes.
If he calls with the suicide ploy again, tell him you are calling emergency services, hang up and do it. Leave him to those who cope with this sort of thing day after day, and in the hands of God.
God bless