Is there anything I can say to him (that would not be pursuing or desperate in nature) to make him see that he cannot possibly "try" with me as long as he is in contact with her?
Barbara,
Has your husband SAID that he's willing to try? I didn't see where he has, and his actions clearly say the contrary. I'm a big believer in "no-contact/transparency" agreements, but unless and until your husband gets to the point where he's saying "I'm TRYING, but I just can't get OW out of my system," there's not much you can do other than work on YOURSELF.
Have you flat-out asked him "Are you willing to end it with her and come back and work on our marriage?"