On face value, it is saying that a woman must remain with her husband as long as he lives. She made a covenant before God.

But if she hears this, having been saved after the marriage to a man who has been married before, her covenant is invalid then.. that is what you are saying. Am I undestanding this correctly?

We are also commanded to stay with unbelieving spouses, but if that unbelieving spouse is divorced, than that command is null and void then right? Is this what you are saying?

How is this an example to the unbelieving spouse? Are you suggesting that there was divorce en masse among the gentiles that Paul was teaching this to? Or are you assuming that even though divorce/remarriage was rampant at that time as well.. that there were no couples that were in what you call "adulterous remarriages?"

I hope I made sense.
Michele