Leaving my husband....

We have been together for almost 15 years been married 7 years, we have 4 kids together. My question is ..... when is enough ENOUGH? I don't even know how to end things with him because of his narcissistic ways. He gets mad at the littlest thing and literally everything. We are dead broke at the moment and it ends up being my fault, EVERYTHING is my fault. Sometimes I don't even know why hes mad or in a bad mood. We've had some bad fights in the past where he would just say he is done and we should just go our separate ways and I tell him that I'm ok with that but then he ends up acting like nothing ever happened. My kids want nothing to do with him either. He will find anything to yell at them for. And my oldest who is 12 can't even open her mouth when he's already talking down on her or judging her for the stupidest thing. My only reason at this moment dor staying with him is because he is the only income we have and it is difficult in this economy as it is and we are barely making ends meet. We are -$200 in our bank account and we have absolutely no savings. I have a way out with my parents but with 4 kids and 2 that are Autistic makes me think it's not possible. 😞