During much of our SSM I actually saw myself as being more HD--after all, my H was the one who'd given up on having sex! It appeared to me that whatever went wrong was his issue (he couldn't bring me to orgasm, he got me all upset when I had been prepared to make love that evening, he had rejected sex a few times so why would I bother to initiate any more, his foreplay was too rapid or repetitious, which made me feel he was only thinking of himself)--I really did not see myself as LD, but as Thwarted Drive. And I didn't really connect it with the abuse at that point. The lack of sex sometimes bothered me a lot, but I didn't know how to talk about it or improve matters.
Your whole scenario about your wife's "airtight logic" when you bring up sex is exactly how my H operated during his depression to make it impossible to have conversations with him. It's a soul-killing bubble to live in, though, and believe me she's not HAPPY to have trapped herself there, even though she's terrified of anyone popping the bubble right now.
You ask about motivations for preserving an unsatisfactory marriage--these include all the reasons you gave, but the worst loss would have been the sense of exclusivity we had when we fell in love--divorce would have put an end to any possibility of rekindling our relationship when it WORKED. The thought of any one else meaning as much to H, or him sharing his intimate feelings with another, was excruciating.
Face it, a divorce rips apart your known world, facing you to confront all the mistakes and weaknesses and failures and defenses and denials which led to this imperfect result. Even in the most amicable situation, it strips you bare. That's why people who are hiding from what they're refusing to deal with shrink from the thought.
