I have a bunch of answers here!

1. I am no expert on staining developers. I don't use them. So, the tests that I have seen were run by others and were merely reported to me directly or via others. Sorry. However, I do know that some stains come from quinones or quinones reacted with gelatin. Chemically, quinones are destroyed by Sulfites. So, there is a possible clue. And, Sulfites are (IIRC) more active in this regard at acid pH.

2. TF-4 is about pH 8.

3. Many films develop pinholes regardless of process. The pinholes are latent in the coating in the form of bubbles in the melt and soft coatings. During processing, in some workflows, the pinholes "burst" leaving - well - pinholes.

The last report I saw that was official regarding pinholes was in the 50s and was written up by George Eaton. Since then, AFAIK, no Kodak or Ilford film has been demonstrated to have them.