I can second one nugget buried in the long original post. That is the use of benzotriazole to reduce base fog in color papers. I have successfully used 5mg/L BTZ to eliminate slight base fog from some Kodak Edge paper, printing with like new results. I also added 5ml/L h2o2 to the mix bump up the contrast a bit. I also eliminated quite pronounced yellow base fog from some Crystal Archive type C, but experimentation there is ongoing as the resultant print is quite flat.

We all benefit from unconventional approaches/tests like these.