LOL, I don't think you are a "head case." *I* am saying that it's not clear to me what is going on but we are all a bit mystified at this point. It sounds frustrating. I am PG sensitive and used max VG and distilled water, and I will say my sensitivity really only hit me full on once I "stopped" dual use. I coughed a bit before but always just ascribed it to dual use, not a PG sensitivity.
I DIY and have just tasted my first batch of PEG400 mixes, and I tested myself with it before mixing, so I knew I wasn't sensitive to *it* and am glad to have something that I can used to minimize some of the fog. I suppose it's potentially part of your problem I guess my "mystery" would be "how can someone work in a vape shop surrounded by PG/VG and etc., and only be sensitive upon vaping, but I guess it could be a "dosage" issue as despite clouds and etc., inhaling second hand vape is FAR less invasive (as far as dose) than actually inhaling. I can tolerate PG up to about 8% or so, after that it gets bad. It's not so much a "true" allergy as a sensitivity, and sensitivities can develop over time, so it MIGHT explain your situation....
I just don't want to give you any "wrong" or potentially harmful advice, since I'm not a doctor, so please take my comments as "My" experience only although if any of them are helpful, well, that's great. Etc.
But yeah, it's complicated for sure... Could be a LOT of things. I think the focus on the metal might be valuable, and I think that is being suggested because we are all imagining you in a "e-liquid" rich environment all day.... But, it certainly could be a matter of dosage.
I don't know what I look like when I vape, but no one's ever commented about it. LOL. I'm sure you look okay, but then again, I haven't seen YOU vaping, so it might be horrendous, who knows!! LOL I am again, kidding.
But I do hope you get to the bottom of it. I think you have some fruitful avenues to explore now, at least I hope you do
Anna