Where do I even begin?

My husband and I have been married for five years and have 2 young children together. I am 100% certain that I want a divorce. He completely ignores me and will not work on our relationship at all. After trying to talk about it for an entire day recently, the only reason he gave me as to why we shouldn't split up was that it sounded expensive. I told him again that I no longer wanted to be married and he threw a tantrum. He told me I would be ruining our children's lives, that he would make it as difficult as possible for me and threw his ring at me. He also said to not talk to, email or text him for any reason ever again, despite me telling him that we have many things to figure out. Then he came to me and told me he really wanted to work on things and he was different for about 2 days and it's back to us living completely separate lives--we're basically roommates that raise children together.

Neither of us can afford our house on our own so we'll end up having to be foreclosed upon or short sell it, but other than that the only other thing we have jointly is a car loan (on a car he will keep). I have no issues with equal custody nor will I try to get any support out of him.

So, yeah, where do I begin? I'm less worried about the legal divorce part than I am about how do I get this going and get a place of my own? Neither of us really have family we could stay with, nor would I put the burden of me + two young children on anyone. He's going to be horrible about this, I know it. Do i just open my own bank account and move half our money into it and then change my direct deposit to that account? I've asked him to leave before and he says awesome stuff like, "YOU Leave." or "Get the F out then." Nothing is ever productive with him. Should I just consult with a lawyer or something? I know he won't be able to afford one so I'm hoping to get him to agree to everything without having to spend the money. I just don't even know what to do first... help please