CFS is likely to be multiple subsets.
I think you are calling it "subsets" and I am calling it "sub groups" but in either case, I think we are talking about the same idea or concept. And we are definitely on the same team and I respect all of your posts that I've ever read.
If there is a subset that is autoimmune with MCAS, multiple auto antibodies causing neuromuscular, breathing, and autonomic issues than this is my subset and I have ME/CFS but minus the immune deficiency part and minus anything that I would label as malaise or PEM (as I understand the concepts).
But if what I have is a true subset than I have ME/CFS. I just know that anti virals did not help me at all and I think that IVIG and RTX and things to reduce the auto antibodies are the right course for me (if I can tolerate them!) and my absolute biggest improvement has been treating the MCAS.
I can now eat (with MCAS meds of course) dark chocolate with cranberries and almonds in it with no reaction and last summer, this would have led to potentially fatal anaphylaxis!
So I think the OP's Doctor is really on track but the question is if he runs all these tests, what does he do about it? What are his ideas? I don't expect him to perform a miracle b/c the science is not there yet. Am just curious what his approach would be. Thank you to the OP for the PM's which I hope to read later today, am so behind again!