Their relationship was built on trying to help each other with their marriages, as strange as that sounds. But in the process things went way too far and they fell "in love".
You are only ten days out. So take a deep breath and do not do anything rash.
Just stay calm, talk to an attorney so you know your rights, and see your counselors to know if the marriage can be saved.
As for helping each other with their marriages.
That is a very common profile or "type" for someone prone to an affair.
These type of people insert themselves in the marriage, with the claim of trying to counsel the other person.
They then both start revealing personal details and complaining about their spouses. It is a very common pathway to an affair.
The complaining also creates a negative mindset of the marriage, often where there was none prior.
So, it may sound odd, but the "helping" thing is very common.
Going forward, if you hear of some opposite sex friend counseling your wife, claiming to want to help her save her marriage, be very wary of that person.