Haven't posted to you for awhile, but I continue to follow your sitch...
My opinion here may not be popular, but it seems to me that your DH is going to cogitate and oscillate back and forth between you and the OW because he KNOWS that YOU will put up with it and will always be there to fall back on....wonder what would happen if that were to change a bit?
My sitch wasn't nearly as intense as yours, but my H didn't pull his head out of his backend until I gave the impression that I was DONE waiting around.
I also find it hard to imagine that this is EVER going to be over if he has to SEE her on a daily basis. I personally think this is what has kept the scenario going for sooooo long.
I don't know if you are up for ultimatums, as you must always be ready for the answer you didn't want, but if I were gonna issue one, him changing jobs to get away from her would be the one I would be soooooo tempted to issue.
I know, bad d'bing...but I swear, my sitch didn't turn around until I decided that the limbo I was in was worse than any thing else could possibly be.