TH, sounds like you answered your own question. "I will not share my life with a wife who is cheating on me" (boundary)" Yes this is definitely a boundary.
If he said that he would not allow her to see the dogs, come home, etc. as a result of it, then that is fine because it is a consequence of her crossing the boundary.
But if he just does it because he's pissed at her, then it's not a boundary.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.