the unknown is scary
Oh yes it is. It can be quite paralyzing. I think that plays a big part in your hesitation. He sounds a lot like my ex, it took me too long to realize anything was better than that. Even the unknown.
I struggled greatly with my fear of the unknown. And then it hit me that life is simply one great big unknown no matter what you are doing with it, your station in this world, how happy you are or sad. You live the unknown every day. In any moment life can give you it all or take it all away.
You will have to work on the fear surrounding the unknown. And leaving is never an easy decision to make let alone execute. Its a double whammy to the senses.
You did the right thing to deescalate the situation. I know it must leave you feeling a bit disingenuous but thats ok. You are in a situation that calls for it. His behavior leads me to believe that he is extremely capable of taking this and turning it into dangerous situation. You have to protect yourself. Even if you have to fake your way to safety.
I agree that you need an exit plan. Like, yesterday.
I don't think you should bring it up with your friend there. I think that's a terrible idea for two reasons.
One. He doesn't need to know anything more from this point. Seriously, you saw what that led to, forget about him being decent, ITS NOT GOING TO HAPPEN. If you are done, he doesn't need to know. In fact, he already knows, he just bullied you into taking it back. Do not give him that chance again, do not give him a chance to escalate it further.
Two. Doing this in front of your friend will most likely add fuel to his range. I think it will backfire in the worst way. As soon as she's gone and you're left alone with him. Honestly, I don't see this going well. I would advise against this.
What I advise is act first, think/feel later. Quietly set up your exit. Its hard to think about all the ducks you need to line up, but we can help you with that.
First thing you need to do is secure a safe place to go. With that person knowing this could potentially be an extended stay. Six months or so? I don't know, how ever long you forsee becoming stable enough for your own home.
You might not want to set any alarm bell off by moving money just yet. Not large sums anyway. Go ahead and open your own bank account. They might send you mail so you will want to look out for that. Sometimes a deposit is required. Call ahead to the bank and find out. If you can't transfer money from your existing account, every time you go to the grocery store get cash back how ever much you can at a time without raising suspicion to fund this.
Get this far and you're halfway there. After this its your own will that will take you the rest of the way. You'll know what to do.