Hi Paige,
Your situation is most unfortunate. It seems that you married a control freak who misuses the Bible to support his delusion. Don't sign any post-nuptial agreement, and don't even discuss one. Rather, consider using the tool over which you have control: physical, financial, and legal separation. He can go on living his deluded little life, and you can live yours without his interference. Plus, that will diminish the likelihood of children, who should
not be brought into such an unhealthy relationship. I can't counsel divorce unless he becomes violent or cheats on you, but separation is fairly easy to accomplish as long as you have financial means to take care of yourself (or family support to do so).
I would offer one warning: if you are going to consider separation, make sure you clearly lay out the requirements that must be met before you consider reconnecting. At the very least, a demand that he breaks all linkage with his old church, simply because his ex-gf is there, is warranted. Counseling is also a good idea, for both of you, separately (for now); I suggest you take a look at the videos with Patrick Doyle on TheDoveTV's YouTube channel.
Your marriage is important, but not more so than your self-esteem and biblical convictions. At this stage, your marriage can be healed and restored.