first my suggestion is take a deep breath.
second understand that just because a treatment provider uses wording like parts, compartmentalizing, separation of emotional and non emotional and so on does ..........not.......... necessarily mean you have DID.

- Thanks for this. I've been reading up on family systems/parts therapy and it sounds like these are useful approaches in a variety of contexts.

you stated your therapist seems to have wild theories about what happened to you... if you mean he is telling you that things have happened to you that did not, thats called therapist causing someone to have false problems and false memories, its actually a disorder where a therapist can get arrested and prosecuted for.

- He's not putting words in my mouth, really, but asks questions, makes comments to try to open it up for me. We sort through my nightmares and feelings and find patterns in them. I always thought dreams were just dreams, and that feelings were fleeting and unrelated to what's real. He suggests that my dreams are re-playing a version of personal history, and that version is incredibly dark and brutal. It's weird, to think these images might have any basis in reality. I thought everyone had dreams like this, but they're quite disturbing, in the light.

your confusion on whether you have distinct parts related to dissociative disorders .... well theres an easy way to solve this one.. you can help you get set up with psychiatrists and medical doctors and so on to do all the different tests.