Spousal support VS alimony

i separated from my ex-husband last September. We had a separation agreement signed but wasn't drawn up by an attorney and filed with the court. I was told it amounts to nothing; is that true? He made a new agreement. He's the one with a good salary. I am waiting on disability decision and cannot work. He wants to cut what he's been paying down by $500 a month. Cut my health insurance when enrollment begins in Jan. Take the car in his name but I've been driving since 2014 at the one year date of separation along with stopping all spousal support at that time. He wants to do an Internet divorce. Also he filed joint taxes but separated and kept it all. Also security deposit. Would I be entitled to half of that? I think he knows if I take him to court he'd be paying a lot more than he does now and probably alimony after divorce. So he's trying to make me sign his "agreement " to rid him of all responsibilities. My friend set up a Go Fund Me for me so wouldn't get evicted. That's how desperate the financial aspect has been. The mental abuse has been awful. He is Bipoar & Narcissistic. Right now he's being calm but I'm sure soon he will not. Especially if I don't sign