My wife would probably decide to follow me - but there's a chance she might not, and I love her way too much to risk losing her.

I'm just going to focus on this, because if I were in your position it would just loom over everything.

My wife made me swear not to keep secrets from her, because of her personal history with an ex. But even if she hadn't ... that's just too big and too relevant to your relationship. Having a secret like that damages your relationship, even apart from your own painful awareness. It just flies in the face of core values of marriage, or even friendship. It's disrespectful to her.

You have a lot to lose. But you also have a lot to gain, if you can repair this break. Are you (ex-)Christian? If so, she should at least be able to stay married, given what the New Testament says about divorce. Being in open disagreement would feel worse, but I don't think it would actually be worse, it would actually be a closer relationship. And as you imply, that could be temporary. Which means you'd have to listen to her attempts to bring you back into the fold, with a mind as open as you can stretch it, and go over the whole religion question all over again. An ordeal, and a steal at twice the price.