NPD. Desperately need Psychiatric advice?

I have just found out that my husband has Narcissistic Personality Disorder. I have been married to him for a little over 4 years, and in that time it has seemed his goal is to destroy my self worth at any cost, even using our children as a weapon. If you know anything thing about this disorder there is a lot more to it. For a long time he actually convinced me that I was completely worthless. I was afraid that I would become so depressed that I wouldn't be able to carry out my everyday obligations and raise my children. I even thought about ending my life. I took some time to reevaluate myself and finally came out of my depression realizing that it is not me with the problem, but him. I was relieved to discover the disorder confirming that it was not me, but at the same time in despair. It is next to impossible to treat this disorder. I am a Christian and take my vows very seriously, (for better or for worse). The other day he threatened to hit me, and I believed him. I feel my emotional and physical health is in danger. If there was any way I could help him I would, but I don't think there is. Should I stay in this abusive relationship with almost no hope of things getting better? or Should I stay with him for better or for worse?