Why do you specifically ask for men's opinions?
Anyway, here is mine: Your husband is having an emotional affair with this woman and the more he gets involved with her, the less emotionally connected to you he will be. The chasm is growing on yours and his emotional connection and the very fact he won't stop what he's doing is proof that he values her too much to just stop responding to her.
Does she know you know he's talking to her?
Does she know he is married?
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion