I'm very sorry for all this pain you are going through. I think a lot of people would drop everything and run back, but even if you did the relationship would never be the same in any way shape or form..You have both moved on emotionally and physically .
Have you talked to a Therapist about how you feel? and how you can work through it all and come out the other side healthier?
As for your son, His father is his father ( not your new husband) and why would there even be talk of him to surrender his rights? If accepting child support from your ex bothers you or you don't need the money... why not just put that money into an acct for your sons college education?

Please consider seeing a Therapist I think it would help