Your reasons for hesitating are emotional and rooted in resentment (which is totally understandable). Your reasons for signing are rooted in facts and logic (which, while not particularly satisfying, typically provide longer term stability and security).
His behavior is unpredictable and not under your control -- if he is bound and determined to make your life hell he will find a way whether you sign right now or not. I say, take what you can get in writing now and work on letting go of those resentments for your own well being and peace of mind.
You've been through more with this man than most of us can even imagine, so I know how difficult it can be to let your brain rule when your heart so wants some level of justice for all of it. Sending you many hugs and lots of strength.