i personally haven't done any DBT, so i can't help you there, but have you had any consideration about taking a short break from your T?? this sounds incredibly challenging and painful for you right now and i wonder if trying to put on the brave face and trudge through these sessions with your T is causing more harm than good?? perhaps having some time and distance away from your T will allow you time to mend your heart and mind from the repeated and triggered reenactments of grief and pain that this 'relationship' seems to be keeping you stuck in.

when therapy got to a similar stage for me with my ex-T, having a six week break afforded me the time to help me focus and see things from a new perpesctive. so upon returning to sessions with him, i had a new sense of confidence and a definite answer to the direction i wanted to be heading in my therapy and in the relationship with my T.