Fidelia's posts are all right on the money, there isn't a lot to expand on (And really Fidelia, your as wise a soul as any!).
I do question the sex bit as well. ITmay very well be that he is tellig you the absolute truth, I won't say that he's not! I will say with absolute certainty that in my experience, denying those attractions and refusing to act on them is VERY different than not having them! I can also say that never, not once ever, have I wanted to kiss a girl I was romantically interested in without the desire - whether or not acted upon or even intending to act upon - to go further being present.
I don't want to upset you or call your husbands integrity into question! But if this is going to be sorted out, he needs to be honest with himself as well as with you - because you ca't be honest with ANYONE if you're not honest with yourself!
As for you coping... Well, first of all, no more "small hearted" crap, LOL! The fact that you're even trying to understand these things - much less going to a place like these boards to gain perspective and advice from people who identify as yourhusband does - speaks VOLLUMES to your character and BIG heart! Would that my exes were so desirous to make things work (OK, not true, because then I might have missed out on Violet and Anne, which is not ok with me at this point, lol). The big question is, do you feel that this situation detracts from his attentions where you're concerned? If you can honestly say no, that you do not feel that under any circumstnaces he would leave you or lessen his interest and attentions for you, well, then maybe work on supporting what may be of tremendous benifit to your relationship as he will likely gain a tremendous level of appreciation and love for you as he recognizes that you are "letting him be him". I didn't put that very well, I hope the point came across right. Conversly, if you feel that his involvement with her causes him to lose interest in you or detreact from your relaationship, well - he's not poly s we here tend to view it! The whole point of this thing is that it magnifies and multiplies the feelings we have for each individual partner. I know that's the case with my situation - I loved Violet so imensly that it almost hurt - and when thing starte to come together with Anne, my love for each feeds off the other and my feelings for both are increased exponentially! If he's like that, than you will know love from him far in excess of what you thought possible as things progress with her. "Love doesn't divide, it multiplies" - Robert Heinlein Ergo, if it divides, it ain't love!