This is a timely post for me as I've been reading about histamine since it's been coming up frequently.
You're going to have to trust me on this for now but all these health issues start with the nervous system. Imbalances and dysfunction of other systems including histamine are secondary consequences.
From I gather, I agree with what you say in both points but again we wouldn't have bacteria overgrowth problems or adrenal insufficiency if we didn't have the nervous system problems.
Symptoms. Head pressure and brain fog are nervous system systems. Fatigue seems to be a combination of nervous system and immune system. Itching and hives seem to be more directly related to histamine.
In order to recover you have to fix the root cause (nervous system). Of course this isn't easy. With that said you can't let the secondary problems of these other systems get out of control, but I think you have to be willing to tolerate some symptoms.
Stick around the adrenal fatigue forum for the next few months..