I'm glad that you responded well to the vitamin C.
Since large doses of it have a short half life--does not hang around for long--you might want to try 1G every couple of hours. You might need buffered or liposomal in between meals.
I assume you have to wear a medical bracelet since 40mg HC is close to full replacment. That puts in your life in jeopardy if you don't have it handy.
Have you done followup 4x saliva tests?
Have you tried other upstream hormones--progesterone cream, pregnenolone?
Have you tried adding adrenal cortex glandular?
Are you taking zinc and vit B5. I think these are involved in conversion of adrenal hormones.
I'm not suggesting that any combo of those will replace more than a modest amount of HC but I'd do anything reasonable to try to keep my adrenals from "going to sleep." Supposedly you have to stay around 20mg max HC to avoid long-term damage to your adrenals.
There are many factors involved in "fatigue", adrenals, thyroid. mitochondria, neurotransmitters (look up catecholamine depression), methylation, and much more. Hopefully you've addressed all of those before resorting to damaging levels of HC.
These issues are discussed so often in heavy metal detox groups because HMs affect adrenals and other systems related to fatigue. This was one such recent discussion.
Maybe a year ago there was a discussion in this group about the impact of a particular infection on adrenals and adrenal fatigue/insufficiency. The infection causes depletion of vitamin C in adrenal glands. Sorry, I don't have a link to the discussion handy.