GH - I've been thinking a lot about your situation lately, and despite my greenish tinge from envy, it has had some other effects on me.
The mental picture I have of you and W is of two people who were very close, and loved each other dearly, but failed to keep the fire going after the start of the relationship. In short, you became friends. The problem with men and women friends? We bore the crap out of each other - we've got nothing too exciting to say, because men and women are different critters. You lost your attractiveness to her by being a buddy, not a lover. Happens every day.
So in our comfy, friendly, boring world comes OM. Even if he has little to offer in any other way, it lights a spark of attraction that women love like we love sex - to them, I think it IS sex.
So your situation requires that you BE THAT GUY that can light the spark, and that's what others are urging you to do when they tell you to be a "take charge male". It doesn't mean rapist, it means leader.
Leader as in set the tone for the evening. Leader as in be in charge and decisive. Leader as in decide WHEN it happens by pulling away when she expects you to push forward. Leader as in letting her know that you don't NEED sex, but if she's lucky, it might happen.
Ever here people talk about how the Tango is a metaphor for sex and romance? Well, watch it sometime: the man controls the dance almost absolutely, pushing her away once for every time he pulls her forward, and at no time submitting to her until the end, when she submits as well. That's what good sex is: it starts days or hours before the crap in the porn movies, and has little to do with what people SAY - it's all about how people feel. Unless it's just crappy sex, which is masturbation with a partner.
Your poor wife is guilty and insecure and scared of herself and your feelings about her, and probably has some performance anxiety of a sort - don't let it get you down. You can't talk your way out of everything.

If you Tango fifty times before you get to finish one dance, don't sweat it: It's the tango that counts, not the end of the song.....I always knew this and forgot when I fell into my black hole these past few years.

God, I miss my wife.

Good luck.