Suicide threats, call 911 there are professionals that can deal with that much better than we can. Called them twice on my son after threats and once they put him in psych ward for 72 hours for observation.
To keep him from manipulating you you MUST set clear boundaries for YOURSELF. Sit down calmly and clearly decide where you will go the limits to oour own behavior concerning him. Then it it much easier than trying to sort through an addicts BS at the time of their pleas and abberant behavior. Set your boundaries based upon your values, not base upon your needs and wants.