I saw Dr. Kaufman, when he was at Open Medicine. I have a huge amount of respect for him.
The problem is, they don't contract with insurance companies (because of the way insurance reimburses, they're not paid for all the time they invest in your care) and that means going to them can be very expensive out of pocket for just the visit. He'll listen, explain well, and be very thorough. You'll walk away feeling like you've really been heard by a competent physician who sees you as a person (that alone is worth a lot). [To the extent you have the energy and time to educate yourself, that will help you ask questions and to evaluate and understand what any doctor tells you. ]
I think Dr. Kaufman is better than many doctors at seeing the big picture. Dr. Kaufman will certainly test for lyme if your symptoms suggest that's a possibility - it's definitely something he runs test for with ME/CFS pts, to eliminate lyme as an underlying factor (I didn't have mold issues so can't speak to that). Don't assume your past diagnoses are necessarily correct. I always think about any diagnoses I get through the lens of how much scientific evidence I think there is for them, how well I match diagnostic criteria (if there are good criteria), and how much I trust the doctor's ability.
When I was searching for a doctor to determine if ME/CFS might be my problem, I was very aware there are a lot of people out there, practicing medicine, coming up with all sorts of diagnoses, who just aren't competent. Despite trying to avoid people like that, I did come across a few - and ran far away once it became clear. Part of the problem is there was so little funding for ME/CFS for so long that we had very poor research on it. That's still the case, but at least a little money is going into it, and there are good scientific studies being run.
Dr. Kaufman in my opinion was very competent, very scientifically based, looks at all your issues as a whole. But, he's limited by our current scientific understanding of specific diseases, limited by the available tests. He did mention MCAS as a possibility for me, but it wasn't clear at the time. I haven't seen him for a few years as it got to be pretty expensive and aside from managing CFS, there wasn't much in terms of treatment. There isn't a cure for ME/CFS, but there are ways to manage it to keep from aggravating it, and steps you can take to keep your body stronger and healthier.
It seems like it's equally difficult to find a doctor who understands MCAS from a solid scientific foundation as it is to find a doctor for ME/CFS. I have autoimmune issues that the CFS doesn't explain (one existed before I saw Dr. Kaufman and a new one in the last few years). The ME/CFS diagnosis doesn't explain them, although since the immune system can be disordered/dysfunctional in CFS, my various issues are not likely completely independent. It's just not clear how they're linked.
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Not to overwhelm you, but here are some resources you may find helpful. They're geared more toward ME/CFS and related diseases/disorders.
This is a 12 minute video of Dr. Kaufman reviewing diagnostic criteria and management of ME/CFS (part of a continuing education module for health providers)
www dot youtube dot com/watch?v=RC9TjgE_PlU&t=105s
This is geared at doctors but understandable to patients. However, you may not fully understand certain terminology and think that does (or doesn't) apply to me ... but if you learn more, you might change your mind.
The Bateman Horne center has some really good videos for ME/CFS and a few other issues here:
https://batemanhornecenter.org/education/videos/ I haven't seen Dr. Bateman myself, and it's been difficult to get in to see her as a patient for over 5 years, but if you're near Salt Lake City, she might be an option - she had a wait list when I looked a couple years ago. She was on the 2015 Institute of Medicine committee that US HHS charged with developing evidence-based clinical diagnostic criteria. This is their (very long) report:
https://www.nap.edu/read/19012/chapter/1
Anthony Komaroff had a 2019 article in JAMA: Advances in Understanding the Pathophysiology of Chronic Fatigue Syndrome
Lab tests: Kaufman orders an extensive list of tests. All of mine could be done at Quest Diagnostics (and I that was what Open Medicine used if they drew my blood in their office - I suggest always asking if getting the best insurance coverage (lowest out-of-pocket expenses) is important to you).
If your insurance provides good coverage for lab tests done at Quest Diagnostics, those might be covered reasonably well (they would get very expensive if you didn't have any insurance coverage at all because the cash price is usually much higher (7-8 times on average, based on my own experience with 2 different insurance companies although both part of Blue Cross/Blue Shield system) compared to what the "allowed price" - what the insurance company contract with Quest allows.
Quest can do blood draws all over the US - your doctor can send you the lab requisition and you take it in; Quest will call the office if they need to clarify which test (and the lab requisition can actually be on another company's form). For a long list of tests, I'd suggest dropping the requisition off a day in advance so they can get everything clarified. (In theory, doctors offices can submit the requisition directly to Quest if they have an account; in practice, that doesn't always work well - the Quest station cannot always find it - so having a copy of the requisition can help.) Quest definitely has its problems, especially where billing is concerned and getting a hold of someone to resolve problems, but I pay so much less out of pocket that I put up with it; I've also learned how to better navigate their system, from billing to the stations that draw blood. Note that Quest will try to get you to give them a credit card number to cover an "estimated" price at the time of blood draw - I never give them that. I tell them I wait for the bill - and their "estimated" price is always much higher than what my insurance company determines my share is. [It's possible they wouldn't allow someone without insurance to refuse to give them a credit card number - but I'd advise trying to not give them one up front.]
Note that a lot of insurance companies, certainly ones that are part of Blue Cross/Blue Shield, don't cover Vitamin D testing - and those tests can run $150-200 or more if you pay their "cash" price. If the insurance company decides the test is "not medically necessary" (which BCBS does for Vit. D testing unless you meet a narrow set of diagnostic criteria), then you don't get the insurance company's contracted rate - you pay the much higher CASH price. I learned this the hard way - and now always decline Vit D testing.
And offering other options that really work