I get the new therapist part but how does your potential divorce hinge on which of you the therapist keeps seeing? Why would your marriage be salvageable if your therapist says he'll keep seeing you but not if he keeps seeing your husband?

I think even if it were possible for a T to have iron-clad boundaries, to somehow store your information and your husband's in separate non-communicating parts of his brain, this would not be workable. Your husband, whether consciously or not, appears to be trying to sabotage your relationship with your T. I think that, for me anyway, the doubt created by toxic little nuggets like "T says I have to stand up to you" would poison my relationship with my T and make it unworkable.