great poem firstly...
and threatening suicide in a relationship is far too much i think.
when i got married we swore not pull that shit on each other, and we didnt... there were times that i would catch myself starting heading that way, but i had to stop myself as i expected the same and understood why, even as a angry hallow expression or w/e.
IDK yalls situation and everyone is different, but - maybe after this settles down lay it out, and explain that you wouldnt/dont do the same and explain further as to why... with examples.
there is only so much you can do about it either way honestly, sounds like a point to look at what you want, and feel what you can honestly expect from him, and what you honestly have to give for now. no matter who he was with, or what the situation; if some one is capable and at the exasperating point where they feel there is no return, it would be done no matter what the environmental situation was or path of life chosen.
if this is becoming a habit a 'wild card' to pull, something used that he knows will get into your head,,, if thats the case then my advice would be simple - tell him to //-/ off with it.