Oh God - your post is somehow one of the saddest things I have ever read. Please believe it wasn't your fault. Suicide is a tricky thing... I know that the generally received opinion is that suicide is
not a selfish act and that the sufferer cannot be blamed for it, but I think it can
sometimes constitute a continuation of abuse (albeit in a very tragic sense that also hurts the abuser) and I think that's what happened here.
Your story made me think of the suicide of the author of David Foster Wallace, who was a great writer, but also an abusive asshole. He was clearly very troubled and unwell, but also did some inexcusable things to his partners (attempted murder of both a woman he was dating and her husband; smashed and thrown objects; stalking; etc.) and he eventually killed himself.
I think what David Foster Wallace said about suicide long before he actually did it was true:
The so-called ‘psychotically depressed’ person who tries to kill herself doesn’t do so out of quote ‘hopelessness’ or any abstract conviction that life’s assets and debits do not square. And surely not because death seems suddenly appealing. The person in whom Its invisible agony reaches a certain unendurable level will kill herself the same way a trapped person will eventually jump from the window of a burning high-rise. Make no mistake about people who leap from burning windows. Their terror of falling from a great height is still just as great as it would be for you or me standing speculatively at the same window just checking out the view; i.e. the fear of falling remains a constant. The variable here is the other terror, the fire’s flames: when the flames get close enough, falling to death becomes the slightly less terrible of two terrors. It’s not desiring the fall; it’s terror of the flames. And yet nobody down on the sidewalk, looking up and yelling ‘Don’t!’ and ‘Hang on!’, can understand the jump. Not really. You’d have to have personally been trapped and felt flames to really understand a terror way beyond falling.
But I also think that what Wallace's friend Jonathan Franzen said about Wallace's suicide after the fact is also true:
The depressed person then killed himself, in a way calculated to inflict maximum pain on those he loved most, and we who loved him were left feeling angry and betrayed.
To prove once and for all that he truly didn’t deserve to be loved, it was necessary to betray as hideously as possible those who loved him best, by killing himself at home and making them firsthand witnesses to his act.
It's a very tricky thing cause it's tied up with the thorny issue of to what degree someone who is mentally unwell is responsible their own abusive behaviour? And to what degree can suicide be seen as a selfish, or intentionally hurtful act? They're unpleasant questions to address and the kind that I'd be crucified on Tumblr for even raising, but the fact is, that even if the unwell person is so unwell that they can't be considered responsible for their abusive actions,
that doesn't change the way that their actions hurt those they lash out at nor the legitimacy of that hurt.
It sounds like you ex was suffering a great deal and maybe that could help you forgive him, but it sounds like he also hurt you enormously in abusive ways and maybe that can help you forgive yourself, as abuse is never the victim's fault.