It is not your fault. He is the one who treated you like that, I can't see ANY reason how this can be your fault. I think at this point your mind is trying to take over and play "damage-control" to save your emotions and feelings towards him. It's a cruel thing that our minds do to us, I've even had it happen to me. Something happens and the first person you see fault in is yourself. You apparently liked him at one point and you don't want yourself thinking that this was his fault. I've seen and heard of this before, I actually went through something similar myself. I just want you to know that this is in NO way your fault. Please don't let this bring you down hun. Keep your head high and try to put this guy behind you, you deserve better than him anyways.
You deserve a guy that truly cares about you and loves you with all of his heart and soul, not one that threatens to kill you and hurt your family.
I know it might be hard to believe after what happened, but I honest to God can't see ANY way how this can be your fault. He even threatened to kill you!
I don't consider a death threat to be something that should be taken lightly, and if you ask me it certainly doesn't convey the message of "I love you."
I guess what I'm saying here is to not beat yourself up over this. I know it's tough and you might feel bad about what happened, but you shouldn't let a guy like that bring you down. Here's my brutally honest opinion; I think that after he got you into the relationship (by acting like he loved you and such) he got the mindset to become controlling and oppressive as to keep you trapped in the relationship for as long as he wanted to. I think that's why he threatened to hurt you and your family if you didn't talk to him. I think that he wanted one last chance to make you feel so so so bad about yourself (to put himself in a position of power over you) that you would feel like the only way to escape the bad feeling was to give into his trap (take him back again). Confusing? Probably, but that's part of the game that some people like him play.
Long and short I'm glad that you didn't take him back. I'm proud of you for not doing that. You deserve better than him.
Hope it helps and if you want/need to talk more don't be afraid to say so.