Lost, are you both in individual counseling as well? Often after an affair we all jump into marriage counseling, but so much needs to be done individually.
What your husband will have to address, is friends don't help friends destroy their lives. This woman is and was no friend to him. But that is going to be a lot for him to understand and accept. He'll need some help to get there, and it is best done by himself in therapy. I hope he's going.
And I'm so sorry you had to see that video. Oy.