Your fiancé needs help, a lot more help than you can provide. The past violence and the potential for new violence are flaming red flags that all is not right in his head. He also is manipulative, using the threat of suicide to bend you to his will. I suspect that his alcoholism is an outgrowth of an underlying personality disorder and unless he is willing to get help with the mess in his mind, you are better off without him. Leaving him will be painful, I'm sure you have some good times between you. But, without help, he will get worse, not better and you may pay a painful price for your loyalty. At the very least, you need to talk with a professional with experience in such things. There are resources available through this forum, I encourage you to seek them out- quickly!