Have you told the OM point blank that his romantic attentions are no longer welcome and that you have made the iron-clad commitment to save your marriage? I get the impression from your post that you're just "hinting" to the OM that you want him to stop his attention. You can still work with him and talk to him about work stuff. You just need to have an emotional barricade around you. It's quite doable.
Also, if your H won't go to counseling, YOU go by yourself. Just do it. Don't wait for him.
I agree that it can feel humiliating for your partner not to approach you sexually. I'm in EXACTLY the same boat. My never makes sexual advances to me-- NEVER. It seems to me, though, that you're trying to protect your H from KNOWING how much this hurts you. That's why I think you have to go to therapy on your own. YOU are the one who is hurting, so YOU need some pain relief. Don't focus so much on how YOU seeking help might humiliate him. Just take care of you.
