Welcome CptJaneway!
I have depression, not dysthymia, but I also have mild Asperger's. There is a book titled "Cognitive Behavioral Therapy for Adult Asperger Syndrome" by Valerie Gauss that might help your therapist. I bought a copy for my T, and she tried some things from the book. I don't respond 'normally' to CBT, but it may work better for you. The same author has another book "Living Well on the Spectrum" that is written for people with ASD. It has some helpful information in it.
Hope you start to feel better soon