Respect is EARNED, Ken. There is a seriousness that is conveyed, and a consistency to the consequences that kick in, that shape the behavior of the misbehaven.
That hasn't happened here, and I've followed your sitch from damned near the beginning.
Simply put, your wife and OM don't take you or OM's wife seriously, they don't respect you, they view your objections to their illicit relationship as WEAK, and they've been thumbing their collective noses as the both of you all along.