Our sitches are similar (aren't they all?) except that my H has not denied having OW to me.
Since your H has now left the house, I wonder if there is a way you could let it be known that you "know" without actually confronting him. Not that he'd come back right away anyway, but if he does decide to, that would seem to remove one hurdle (him having to confess or keep hiding what happened). Perhaps a note saying that there is no need to discuss it, or deny it, but you do know about <insert OW name>. You don't like it, but have accepted it, and you are praying for him (if you think that is appropriate to say). Or some kind of closing that is just slightly positive (or at lest could not be interpreted as threatening or persuing).
I'm kind of just "thinking aloud" here.
About "exposing" the A... I can see how that worked well for bfm, especially since the work thing seemed to work in her favor. I don't think I can do that in my sitch. I'm sure all of H's work knows, my guess is that it is obvious. OW is somewhat of a subordinate, but not a direct one. He is a partner, she is not, but she has not usually work directly on cases with him, although may do some now. H's firm is riddled with cases of infidelity (but also what seem to be true, faithful, family oriented people - then again, who knows since I thought H was definitely one of them) so exposure at work wouldn't do much. H's parents and sister have all passed away in the past 5 years so he has no family to expose to. H has many friends who he has somewhat distanced himself from (slowly since his parents passed). I will probably let a few of our closest friends know a limited version once H has moved out. His best friend, who he still does hang with some, and may have talked to some, I don't expect to help my cause. I like him, and he likes me, but out of all our friends it would have been him that I would think could have an A (but his would be the one-night stand type, not the soul mate type of A), he has always been a little "sneaky". There is not really anyone for me to expose to. Finally, I don't want my kids to know about the existence of OW (and if I remember, I don't think bfm/fw's kids knew), although I know that is not entirely up to me if my H takes them around her.
So I can see how exposing can work well. I just wanted to give another set of circumstances to think about as you decide what to do in your own sitch. You will figure out what works best for you.
(((hugs)))
Nature Girl M 40 H 40 M 15, T 19 D11 S9 bomb 3/07 (MOW)