Scout, this is all a bit much and you have been such a trooper. It is natural to have these moments and to feel overwhelmed. I'm much older and my kids are older, I have been dealing with this a very long time, and I am very familiar with the legal system and at times I feel overwhelmed by it.
Couple of things that stand out to me.
1. Find a lawyer you trust and then let them do their job. Do not keep changing what your lawyer suggests to placate a man who most assuredly is not thinking about yours or S2's best interest. Try not to micromanage. It will drive you crazy and drive up your costs. Tell him your goal and let him do his job.
2. It may have been your past to have bad experiences with men and authority figures, but it doesn't have to be your future. Use this moment to stand up for yourself and stop worrying about who is watching or what they are thinking. You matter. Your view of yourself matters.
3. You aren't going to nice him into anything. Set clear boundaries and stick to them. That is not mean or argumentative. Don't assume by giving him what he wants he won't retaliate. All he will do is take advantage until you are sick of it, and then he may. Firm boundaries will teach him how to treat you and how to behave.
4. Don't get lulled by him having a lawyer or not having one. It could change at any time. Because he has been abusive, leave it to your lawyer to deal with him.
5. It's very easy to refinance even a car these days. Go with your lawyer's recommendation to free up your credit. Indemnification won't help with that and it is just something else to fight over if there is a problem.
6. If you are waiting with S2 and he doesn't show, then leave after 10 minutes if he hasn't notified you of something unforeseen (take a video on your phone to preserve the day and time). If you are waiting for him with S2, document, document and let your lawyer deal with it.
It's totally normal to feel raw and vulnerable. But it absolutely will pass. There will be as many or more good things in you and your relationship with S2 as there are bad ones that come out of this.