You stated, "Are my sexual needs worth throwing away/splitting up my marriage, the solid and positive relationship I have with the in-laws, our properties, etc. You're talking about all these changes for what... just so dad can have sex in a room where nobody else can see him a few times a week? No, correction, just so dad can have sex with another person in the same room, not just with his Playboy calendar?"
Honestly, if having sex with your wife wouldn't add a thing to your life other than satisfying your sex drive--it wouldn't enhance your love, deepen your intimacy, profoundly affect your sense of sharing yourself and growing in a relationship--then I can see why there'd be no reason to change anything.
Also, you said, "She's been to therapy about it, and, well, it doesn't seem to have gotten our sex life to where it should be. I'm just left with the gut-wrenching realization that in the real world, not all therapy is successful...."
As you've no doubt heard before, therapy can only work if the person receiving it WANTS to change. If you "dragged" her there, it's highly unlikely that she was motivated to change. Making changes to ourselves, facing our fears, is the hardest work we ever do in our lives. After 15 years of showing her that you're 95%-or-so perfectly happy not having her work on herself, I can see that it's unlikely either of you will try to get out of your rut.
