Thanks, Gardener. I do appreciate your words of support. I am grateful to have the wise counsel and support of so many good folk here in the DB forums, such as yourself.
On the other hand, in humility, I don't let myself entirely off the hook with regards to S5's issues. In the past, even when I have held my tongue, I am certain my true feelings about xW's actions do come out, try as I might to suppress them. As a result I have failed to keep my injuries hidden, not entirely, and thus my S's know of the pain I feel from their mother. And that is not something commendable on my part, by any measure.
But I really believe I am now starting to turn the corner on that, learning to put that behind me. I pray that I am, at least.
I will, as you suggest, follow back up on the family therapist groups that I had researched and contacted lat year. (Our parenting coordinator is himself a family psychiatrist, incidentally. But because I have determined that he lacks any conscionable moral convictions, I cannot really employ his particular help. At this point, I'm not sure he has a value system that would allow him to truly understand the implications.)