NP, do you believe you are responding in a way that feels like PTS(D)? From a distance, it certainly looks like it to me, and it's perfectly understandable. While your emotional reactions may be "bigger" than the current circumstances warrant, they make total sense given the trauma circumstances you've been through.

My understanding is that DBT has a good track record of effectiveness in helping with dysregulation stemming from certain personality disorders (which often originate from abuse, but are seen as primary defenses that have solidified into persistent patterns of thought/action.) I haven't seen anything supporting the effectiveness of DBT for active PTS(D). While I'm not a huge fan of EMDR, the one area in which it does have a solid record of effectiveness is as a treatment for PTS(D) resulting from recent trauma. (It's effectiveness in complex trauma of long standing is far less convincing.)

Is your T trained in trauma? Because it seems to me he is focusing on your behavioral reactions to current situations, rather than see your responses as reactions to the barely past trauma. It's like he's seeing the signs, but missing the bigger picture that explains the signs.

I would be very unwilling to go into DBT as a Band-aid treatment. And I don't like how he seems to have decided this is what's necessary for you, despite your misgivings. I would want to get a lot clearer explanation from him on his level of knowledge and why he believes this is the preferred treatment. And if in his explanation he only focuses on behaviors, I would take that as an indication that he doesn't understand the psychology of trauma.