Hi Kells,
I have stuff around feeling powerless that goes back to childhood as well. My mom had BPD, and there was a lot of insanity/abuse/powerlessness in my childhood. It's clear to me that's part of why I got together with my ex, though I didn't consciously recognize that she had BPD at the beginning.
I don't have a sense of feeling "trapped" at this point. Though I did before I walked away from the remains of the relationship 7 months ago.
There are elements of the situation that still require some degree of ongoing communication with her - the major one being our son (my stepson). I've basically been his primary support within the family since she started the affair - it's pretty clear that she jumped into the affair in part to numb her distress at his situation, and that left me as essentially his caregiver (everyone else in the extended family basically condemned him and broke contact). Also, I agreed to her request to go for a walk in a natural area with her every 2-3 months. It's clear that she wants much more contact, but I've maintained my "minimal contact" boundaries pretty readily, refusing all requests she's made to spend more time with me.
Anyway, at this point, for me, there isn't a sense of trappedness or resentment, of being stuck in the situation and being "forced" to watch it go down.
But there is extreme sadness as I watch it. Both in regards to her worsened mental health and, especially now, her physical health - the COPD.
A funny thing... over the 25 years we were together, how I felt about her went through different long phases. There was a long period, after the honeymoon ended and her problematic behaviors became clear, where I felt quite ambivalent about staying in the relationship. Then, in about the last 5-7 years of the relationship, that changed - I came to a place of accepting that this is the way she was, and of loving her deeply, despite that (with a sense of choosing to be in the relationship, despite all the difficulties it brought). Who knows what would have happened if it wasn't for the particular confluence of circumstances that ended it - but it felt like things were gradually improving before that happened.