Who decides what is "fair" in a divorce?

I have been married for 11 years (together for 17) i reached my limit a few years ago and last summer finally had the courage to tell him I wanted out. Since then it has been ago horrible Rollercoaster ride as he goes through the loss of his marriage. Grasping at every attempt possible to manipulate me into staying. Most recently telling me I am possessed because that is the only way a divorce can happen. Ridiculous and ludicrous...but it can just be added to the list of reasons why I am leaving. I proposed that he keep the house, just giving me 50% of the equity we have accrued in the last 9 years. Hoping I can use that as a down payment and start my own life. But after looking at houses it doesn't seem like I will be able to stay close at all. It breaks my heart really...I have been a stay at home mom for 8 years... I can't live with out my boys. So what do I do? I dont know...