Why not get a hair mineral test, see if your copper is really low? Get a TEI one rather than ARL as they will tell you that you have hidden copper toxicty, when in fact, you have copper shortage..taking that amount of zinc will of definitely knocke your copper off!
If NAC works, then Glutamate could be a big piece of the problem, its very common in AF, Chronic-Fatigue-Syndrome and ME...but because the AF 'gurus' dont talk about it, many dont look at it as a way of quietening the anxiety down. This is why they respond to Ashawaganda, Progesterone, Pregonalone etc - they are all gaba inducers, similar to benzos, and what cancels glutamate? Gaba :) If you have ever taken pyschiatric medications, then there will surely be a glutamate connection. Holy Basic is also a gaba herb.
Have you tried taking a simple antihistamine like Benadryl? if so, does you anxiety calm down or get worse? If it calsm, then chloline isnt a problem, if it makes it worse, chlorine may be needed.
I had a similar story to yours, heavy martial arts training, low calorie diet, vitamin C and caffiene as stimulants to keep going..N.O Explode was myh choice of supplement back then!
Email Faith110 about sacylites, she was mental with them till she got better using Adrenal Cortex Extract. But yes strange with high cortisol.
Get on the meditation and gentle yoga, Vitamin C lowers cortisol, check your copper level, maybe add some magnesium. Some things to start with.
There is only one person I would wish benzo withdrawal onto and his name is Osama Bin Laden!