I find it easier to draw boundaries for my own behavior than for other people... I identify what my goals and morals and values are, and then define how I will act based on those values. If people treat me in a certain way and violate my values, I cannot let them be part of my life and still consider those things my values.
For example, respect for others is an important value to me. But, I can not have self-respect if I allow other people to be disrespectful to me. Therefore I will hang out with people who treat me with respect.
Then it's not like I'm trying to control other people. It's just that I am defining what is and isn't acceptable to me.
My ex can act however he likes, however, I will not be a part of it because it doesn't fit in with my personal values. So sad if he doesnt like that. But I have personal boundaries.
Your ex is going to off himself whether you are there or not. You cannot stop a person who is serious about committing suicide from committing suicide. If you are truly concerned, call 9-1-1 and let the professionals handle it.