The rollercoaster and whiplash are hard on you already, and it's difficult when you also see your spouse's unpredictable behavior affect your child
The wildly varying and harmfully intense emotions associated with pwBPD can bleed over into our lives, perceptions, and emotions as well. They do some intense or hurtful or irresponsible thing, and we can get wound up in response -- believe me, I know (my H's kids' mom has many BPD traits and is married to a guy with many NPD traits... I get it).
Getting clear with ourselves about our own goals -- if our own goals are in touch with reality and are healthy -- can be helpful in positions like yours (and mine).
I'm trying not to let myself be angry. I'm hoping that he's honest with this therapist. I spoke with them in advance and let them know my concerns, and his prev therapist's assessment. But I can't control what happens in the sessions, and I don't want to overstep... Is there a way to give this information so that his new therapist has it without crossing a boundary?
You've made some contact with his T already; as far as I understand, anyone can call any T and provide information to the T, but the T can't necessarily respond/comment unless the client has given permission. So some good questions could be:
what would your goal be, in contacting his T a second time? what outcome are you hoping for?
what's the best-case scenario that could happen? worst case scenario? most likely outcome based on track record?
Is the most likely outcome the same as best case? worst case? something in the middle?
So much of navigating BPD relationships is unintuitive; it can help to think in terms of "what is an
effective step to take" based on your own goals, boundaries, and values -- which are the only ones under your control
Hope it'll be helpful talking through things here;
kells76