It sounded to me like you were going to first follow the other advice (tell W you were moving toward sex with other women) ...
WTF? Where on earth do you get that?!?
What Yoyo or I were saying is that if Doc is having these feelings, rather than act on them, instead speak to his W in an open, one-on-one dialog. You know, open a line of communication? To communicate like a H and W should? She can't be completely stupid to think her H is not suffering some increasing sexual tension. Believe me, she KNOWS that the celibacy in this M is not without its impact on her H. Fortunately for her, Doc has been super-exceedingly patient. And if she had any bit of compassion for H she would welcome knowing her H is cares enough to be open with her. If she can't appreciate and accommodate at least verbal intimacy with her spouse, then one has to question just what she expects a M to be.
At the same time, Doc needs to be clear in his own mind what his motives are and should be. If his goal is not to give honest communication of what he is struggling with, to seek her support in dealing with these feelings, but is really more to use as a threat or an ultimatum to W, then I'd say that would be counter-productive and unfair to his W. I am certain that would not be what Doc would intend anyway.
I would agree that it would be delicate balancing act, to convey to his W the depth of what he is struggling with without making it seem like he's just trying to manipulate her, but if that's what Doc decides upon I am certain he would be more than capable of communicating that effectively.