I would read (or re read) DR. I know you say your relationship has not been better superficially at least than it has in a long time. My M was the same way after our original BD about a year ago. After about a month from that day, I thought we were working through things, as things got really well between us. However, it all went downhill months later when I discovered her A. This summer I come to find out from her she never really was giving our M a chance during the time I thought we were working things through.
So I would be wary of 'thinking' you are working on things simply because you guys are outwardly getting along, and going on dates. I say read or re read DR because what stood out to me was the part where after a WAW checks out, she basically quits the nagging, and other behavior which the H thinks of as negatives (and she thought of as trying to fix things) because she has emotionally moved on. The fact she will not quit contact with her OM, and does not give you any physical intimacy really stands out like a huge red flag to those of us who have been down that road.
As for advice on what you should do, I really cannot offer any. I do not know enough about your situation, past and current, to fairly do so. I also know how hard it will be for you to take what you are getting, and make the choice to back off from it. On the surface though, it would seem you need to set boundaries on the entire OM situation. And more importantly, stick with your boundaries. I have a feeling though, I know what your W is going to decide, and I know how much hurt that will cause you. I do think though, she is letting you live with blinders on while she cake eats.
Sorry if I sound negative, I really hope I am wrong and you both are truly working towards saving your M. From what I read though, I do not think this is the case.
Best of luck to you...
Me: 42 W: 32 Married 7 years together 8.5 S1: 7 S2:7 Bomb #1: 09-16-13 Recon #1: 11/13 A discovered 04-03-2014 W filed D 05-19-14 but never served me I filed D 12-02-2014 S 05-31-14 Divorced 5-19-16