(1) It is a great idea to be on the extension when H cuts things off completely, just mute yourself. Him following through on this WITH YOU on the extension demonstrates real resolve. Communicate to him the messages you want OW to hear: he is committed to you and his M, his A was a mistake, he does not want her in his personal life in any capacity, do not contact him after this call in any way.
(2) My guess is that he is in contact with OW, though it is probably her initiating. Has he said he has not spoken to her or emailed her at all?
(3) If I were you, I'd tell him to get back to me when he is ready to make that call with you on the extension. Until then, let him stew in his own drama.
(4) If you do this, there will be stages. There will not be perfect crisp honesty all at once, mostly because H will still be lying to himself a bit. This is normal. I think it is unavoidable. But if you are going to freak at each new revelation in the future and run when he stumbles a bit, give up now.
