My (alcoholic) father committed suicide when I was 23, and one of my brothers - also an alcoholic - came perilously close a few years back. By that, I mean it was only medical intervention which saved him.
I used to work for a suicide helpline. Looking back, part of my motivation was to look at the whole concept of suicide in a safe environment as well as providing emotional support to people in that predicament. I had a brief relationship with a fellow volunteer from another branch. I was worried by his behaviour when drinking and told him I didn't think I could continue the relationship. He then threatened to kill himself if I ended it.
I told him that if his life without me was really going to be that bad, I'd respect his decision - and ended the relationship. I went around for several days feeling as though my head was going to explode; I also contacted the director of the branch that he worked for, to say that I was concerned that he was feeling suicidal and she said that they would do their best to give him the space to talk about his feelings. He was livid. This was obviously not the way the manipulation was meant to go.
Experience of life has taught me that suicide is a very aggressive act, second only to murder. Threatening to kill yourself is as aggressive as threatening to kill anyone else; apart from the 'normal' grief of bereavement with my father, I realised that all the comforting clichés people tell themselves ("They wouldn't want to see you upset" "They'd want you to pick up the pieces and be happy in life!") don't apply when it's a suicide. I knew perfectly well that we were meant to suffer; he even wrapped the empty paracetamol bottles in my mother's nightie for her to find, for example.
It's a long, long time since I've been in that situation; for me, letting myself feel the ANGER along with my feelings of loss and devastation was a key element in moving through and beyond it. I felt guilty about feeling angry for years, too... until I attended a talk given by a bereavement counsellor who said that the anger was actually the healthy reaction.
I think anyone would find that kind of experience disturbing and distressing, but I was also aware that the boyfriend's threat would also be opening up my own old wounds - of which he was well aware. The distress for him was real, but there are more effective ways of dealing with it in the way he did, and I'd have been doing him no favours by allowing myself to be manipulated by it - let alone the effect the emotional blackmail would have had on me.
If you want to recover from this relationship, cut all ties and let him concentrate on his own life, his own recovery. Getting back in contact with him was the equivalent of the first drink for an alcoholic and, as you have seen, the chaos and drama of an addictive relationship was soon back in full flow. It was a slip; none of us can claim a smooth, straightforward recovery. Stop beating yourself up, take in the lesson that this incident is there to teach you, and keep moving forwards.
(((HUGS)))