Just because you have something in writing doesn't mean that he will stick with it. Promises can be broken and that's why it's better to have something written up by a lawyer and signed by both of you. What you need to find out is if there is something called "separation papers" in your area. Also, you need to find out about having the monthly funds from his check direct deposited into your account.
Finances are something that definitely need to be discussed. It is very important that you take care of you and your family because once he's out the door, he's not really going to be there for you and your family. I may be wrong about that, but you need to protect your financial assets as much as possible.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.