A couple of thoughts:
First, I wanted to rebut the idea that there is "an exception to Standing"; Standing is always a choice, and there can never be an exception to making a choice. People have held fast to damaging, destructive marriages, and people have walked away from otherwise healthy marriages.
As far as abusive behavior from an MLCer goes, it does not have to mean that you have to end your Stand, but I believe that, at the very least, you should develop very strong boundaries about acceptable and unacceptable behavior from your spouse at this time. Emotional abuse and manipulation are very good reasons for No Contact if you can manage it, or going dark if you can't, until the crisis is over or until you decide to end your Stand.
In my personal opinion, any kind of abusive behavior would be a "deal-breaker." The Bible teaches that marriage is God bringing two people together to complete each other and be fruitful, but we also have free will and can make choices that are harmful to ourselves or not pleasing to God. Physical, emotional, or sexual abuse would be evidence that the relationship that you are in is not the one that God would have for you.
It sounds like there is much more than simple MLC going on in your life. I would really recommend talking to your therapist about this; abusers and controllers have an uncanny knack for finding partners who will take the abuse. And there is always the danger that abuse will escalate, especially when you start pushing back. I'm a little worried that you think your friend "guided you into an affair"; no one can make you do something like that against your will. Similarly, it's not the responsibility of anyone here to tell you whether or not you should end your Stand, because we don't have to live with the consequences of that decision. You do.
And finally? None of us know with perfect clarity that our actions are the correct ones. Even though I choose to Stand, and even though I believe that my wife and I will end up together, there are too many uncontrollable factors; first and foremost, our spouses. My wife could come out of her crisis yet choose not to reconcile; perhaps she feels I can never forgive her for what she's done, or she never learns to forgive herself. There are the day-to-day risks of the real world, as well; a fatal illness or lethal car crash could end our Stands for us.
The only thing we can do is take this time to learn more about ourselves and what goes into being well, and learn more about what being in a healthy, fruitful marriage entails. Then, if we get the opportunity to work towards reconciliation with our spouses, we can build a better marriage.
Me: 45, Her: 40. Married 16 1/2 years, together(-ish) 20.
Status: BD 8/25/09, she moved out 8/28/10. No talk of D.
Every day is another chance to get it right.
http://www.vachss.com/mission/behavior.html"Counting days won't buy us years" —Wings by HAERTS
"Forgiveness means giving up all hope for a better past." —Lily Tomlin
"When we commit to our lovers, we implicitly promise to forgive them. There is no other way we can live with someone for better or worse or until death do us part." —Dr. Frederic Luskin