I think you need legal advice from a lawyer. At least here, the default timeline only applies if you don't contest anything. You don't have to just agree and accept things the way she wants them. The downside is that it could certainly cost you money. The upside is that it might buy you time.
I agree that she is almost certainly having an affair. But I don't know that you really need to be focusing on that angle yet. Until you are a better option, trying to stop it isn't going to help you, I think. I believe your time would be better spent focusing on yourself, presently.
