start sealing your decals with decal solution such as micromark rather than krylon spray paint
I've produced 100's of decals for customers and seal them with decal film prior to shipping , not one single complaint of a reaction so far.
under about every clear coat you can imagine
get the best compressor you can afford , the ab to learn on can be cheap you will upgrade that before long , but I always recommend not to focus so much on the airbrush more on the compressor, it is often the larger investment and something you will want to be satisfied with down the road
one just before the regulator is needed .. it keeps the regulator clean and trouble free.
any extra is only dealing with potential moisture in the actual AB line.. so a small one at the ab input is popular.
but I always make sure to have one just before the regulator... and that's usually sufficient unless you have a ton of air-line after that
it sounds like some form of depression and/or she is not getting a good nights sleep, good news both are treatable
(my wifes an RN so I hear about these symptoms)