Sending hugs, Meggem. Your lawyer is right; she can draw up whatever you want, but it doesn't mean he'll sign. Even if you gave him _everything_ odds are he wouldn't sign because you're trying to leave.
I get where you're coming from on trying to help for a few months. I covered AXH's for a month after I left. He took a different route: he played the "Woe is me. I can't make it. Look at how much I NEED you." Guilt trip! I was going to make him homeless. And we were renting from his family. He wouldn't have been any happier if I'd paid 3 months or 3 years. I was LEAVING. I was trying to break his control over me. It's pretty much the same reason I wouldn't expect a rational response on the paperwork from your A, either.
Hang in there! Get all the info you need and see what options come up.
BTW, if your name is on the utilities for the house, make sure you get it off of them when you leave. I called all the utilities for the apartment AXH and I shared. All but one were "No problem. Your name is off as of ##-##-##." The last one just said they'd make a note of the call and that I was moving out. They didn't note the account. I kept getting calls when he stopped paying because my name was on the account. After quite a few months, I ended up pointing out that I had my own account with them set up on Day X and that was the date I asked them to remove me from the old one. Then they acknowleged that, but said since I was his wife.... At which point I told them they could call SIL and FIL, because they're his family _and_ the landlords. It was a huge P-I-T-A.