NP, your therapist is only offering what he can think of to augment his shortcomings, but that's not the only solution. I agree with others that you can come up with some ideas for yourself besides DBT. An EMDR therapist, trauma-based yoga or anything to get some good feelings back into your body (swimming, zumba, hiking--something taxing), or trying another group (a 12 step for example). I would trust that he's telling you the truth, that he's worried he isn't helping you; but he's not abandoning you, just looking for other help in addition, and that's a good thing.