Why do I stay?

I have been pondering this question someone posted to me on this site. I don't know the answer.  I know I am paralyzingly scared and that I have always been someone who accomodates people trying to play on a team.  But what do people do to garner enough fortitude to make the necessary changes and withstand the war of the roses that will affect our own children and grandchildren.  How do people know what to do?  

We here have crossed a line this weekend.  I was afraid of Dh.  I got out of the house and rode around for four hours so that he could cool off and so that I could settle down.  His rant was irrational to me and his tone and stance were threatening - he didn't say any threats of what he might do to me.  I realized that I had nowhere to go and no one to go to.  I had decided during that time I must get him, us or me some help.  

All these years I had been taming the beast by compromising myself.   But I am not physically or emotionally able to tolerate what I tolerated when I was younger and I am probably poking at the beast in him by saying what is on my mind and not holding back like I used to.  He is reacting like a 3-year-old who is now expected to be grown up. He is defending his turf of entitlement and I am fighting back. I am not taking his words personally any more. Over the years, I would tell him my boundaries (many times in writing) but they have had no effect. Any actions on my part as consequence were ignored.  He denies, distracts and soothes himself.   He does not care if I am sad, or mad or if he hurts anyone emotionally.

Here are my questions.  I need to put into effect Plan B.  I need some counseling or coaching.  Who do I call?  A LSW, Therapist, Divorce coach, Attorney?  How do I decide who can walk through this with me?   I think we need to separate.  How do I leave him alone in the big house where he is a hoarder when the house needs to be sold?   Who can help me through this?  Should I move out? Should I change the locks?  How can we sell the house without his cooperation?  Shall I close our bank accounts and open new ones under my own name?  I don't have relative or friend who I would impose upon for help with this work I need to do.  I have read that a marriage in this situation should have an intermediary.  How do you find someone?  Can I do this alone?