It's not easy to get a good overview. It happens to me that I think I have a good idea of the main topics and then I just found out about Lupus testing or Copper Toxicity.
Here's a "raodmap" that gives an overview over things to test for with ME/CFS
http://phoenixrising.me/roadmap-for-testing-and-treatment
For me Phoenixrising is most helpful when I figured out a new topic or supplement to then find experiences and information with the searchbar or google. Also if you have a question on a topic you can post and people share their experiences.
Some other health issues that I know of, just to look through and see if something could fit:
-Leaky gut Syndrome/ gut health/ food intolerances
-Histamine Intolerance
- Detox
- Copper Toxicity
-Adrenal Fatigue like you mentioned above also in connection with important calming neurotranmitters
, activation of the sympathetic nervous system and parasympathetic nervous system
-figure out what basic tests to do: mineral or vitamin levels in the blood, Hair Mineral Analysis, neurotransmitter/ cortisol testing,..