What should I do/think?

[Thinker]

From your posts it sounded like he was making settlement offers, making claims about how good those offers were, and asking you to sign.

I wouldn't even start to have these discussions with him until you have talked to a Lawyer and found out what your rights, responsibilities are.

You are at risk of inadvertently agreeing with him on some things that are bad for you in the long term.

I think that you should continue with DBing full force, but in parallel, get a lawyer. Then in response to any of his claims like "This is better than child support" you should just respond "I'll have to check that with my Lawyer.

Protect yourself and your son.