You might want to tell him that threatening suicide is a sheer manipulation, but if he is truly suicidal he must take himself to ER instead of threatening his soon to be ex wife to off himself. You aren’t a doctor so if he is suicidal he needs to see a medical professional.

You aren’t going to resume a broken relationship because the person threatens to kill himself. That’s what mental health facilities and ER are for, they will help him out, or at the very least he could call crisis hotline.

It’s not your job to keep him alive and he needs to immediately stop telling you that