I wasn't quite sure about the dr who told you to quit your job - was it Dr C in MO?
If it was, then I think I'd try to follow his advice.

If it was a different dr, I'd recommend you talk with Dr C & get his opinion. If he's been treating you a couple yrs, he should know your situation pretty good.

If you need the income from working part-time, then you could try working fewer hours to see if less time in that environment makes any difference in how you feel.

Only you know whether the insurance is paying enough to warrent your continuing to work there.

Are you improving on antibiotics?

There are a large number of toxic compounds used in shoe manufacture. The synthetic materials themselves off gas, and dyes, waterproofing, glues, and other finishes are very toxic. Even the boxes the shoes come in likely have formadehyde and solvents in the inks.

Whether or not you are sensitive to these things, I can't tell you. But they are definitely hard on the immune system.

Limiting your exposure would probably help, if you have no other choice. Is it possible that you could leave the job due to the exposure and get at least short term disability? You might check into whether the exposure causing difficulty in your treatment would qualify you.