DnJ, of course I knew that you would say that and you are indeed correct. I have been circling this issue for some time and I guess was ready to face it. Expecting the worst is a protective mechanism, but as you say does have the cost of driving down expectations. I remember hearing of a teacher who was given the worst kids, but was actually told she was given the best. At the end of the year, her kids out-tested the top kids. Expectations often drive the level of our performance.
Andrew, excellent points. Of course, not possible with an emotionally-needy 15yo boy. I think had he been older, I would have pushed the divorce through, sold the house, and gone back to the place where I want to live. It would have been much easier for me to move beyond this stuff. It is still my plan, but a little over 2 years down the road (and getting closer every day).
Given S and his needs and wants, I think the best I can do is just be kind and not project my negativity onto OD, while simultaneously keeping my positive expectations in check. Because I no longer see the desirability of a personal relationship with OD, focusing on aiding his relationship with S (even by doing nothing more than staying scrupulously out of it) is something that feels much more psychologically possible.