So, I've waded through this thread and I'm not sure that I have much to add.
It seems to me you are married to a person that has developed a sexual aversion. I don't think any behavior modification on your part will change that. She dislikes sex to the extent that she knows her behavior compromises her marriage, but she just cannot (and I think it is probably "cannot" and not "won't" change her behavior). She isn't doing it to hurt you or to make you insane. It is just something she cannot bring herself to do.
The good news is you have choices. 1) keep living the same way for the other benefits your marriage provides and take care of yourself. If you do this though drop the begging for the occasional HJ . . . she just doesn't want to do it and it is kind of creepy to me somehow; 2) stay married and get a mistress or go to a prostitute. A horrible decision for many reasons I think, but it is a possibility. As you stated some people live this way; 3) divorce and find a woman that doesn't have a sexual aversion and enjoy a real sex life.
I think the worse choice would be to stay married and to keep pressuring your wife for sex that you know she doesn't want. If you stay married to her, I think at this point (after 15 years of rejection) you should probably just let the sex thing go. You have a wonderful friend and co-parent to your children. Perhaps that is enough.
Finally, no one owes anyone else sex. Even in a marriage. There are consequences for forcing your spouse to endure celibacy, but it is still a choice that every human should have the right to exercise.
I'm a man . . . But I can change . . . If I have to . . . I guess . . .