I am considering divorce, what should I do?

My husband is bi-polar and has some issues either beyond or as a result. He makes bad choices sometimes and seems to have a hard time with dealing with demands of life. I was aware of his issues before we married, but I thought that they were improving and I thought that if we had a new start then things would get better. I also thought that I could help him. The issues have been that he becomes unstable when we argue or if a highly stressful event occurs, he is on meds but still seems to want to have a drink almost every day, and I feel like there is a threat that he will be physical with me. He has been physical in the past and in the past 2 months has threatened me during an episode and kept me from leaving our home. He hit my leg just yesterday. He did not use much force yesterday, but still hit my leg. I had become annoyed with him and had an upset tone with him. He has told me before that if I never yell at him then he will never be physical because my yelling triggers him to become unstable. I do not want this conflict in my life anymore and feel that I am always struggling or dealing with some sort of issues in our marriage. How should I leave if I decide to do so? I pay all of the bills while he is on ssi, but he is on the lease. I have told him countless times that I do not think it is working and that he is too unstable for me to deal with, but he always tries everything to stop me such as: saying he loves me so much, apologizing, acting suicidal, making promises, and saying that he needs me. I also have realized that he becomes more unstable when I talk about divorce and that I have to do this on my own, possibly discreetly. We were supposed to move in about a month, but I need to take some sort of action now and am not sure how to best approach this. I still have many resposibilities to take care of here in the next month. I do not want to leave him with no place to go but also can not keep living like this.