Question

Hello Rabbi. I do not know whether the Rabbi is familiar with this topic, or whether the Rabbi has already been asked about it, so I will preface my question in the hope that I am not burdening the Rabbi. This is not really the main point of the question, but rather the main issue is the force of custom in halakhic ruling.
 
Some claim that following the rediscovery of processing with galls, it has become clear that the parchment we use today for tefillin is not kosher, and that according to the overwhelming majority of the medieval authorities (Rishonim) (and also according to the Shulchan Arukh), we do not fulfill our obligation with it. Only according to Rabbeinu Tam's view is our parchment kosher, but some claim that Rabbeinu Tam, had he been familiar with processing with galls (which was not known before him), would have retracted his view (if the Rabbi wishes, here is an article that expands on the matter https://www.machonso.org/hamaayan/?gilayon=48&id=1445).
 
Let us divide the question into three parts:
 
A. Is the Rabbi familiar with this topic, and could he perhaps offer a halakhic conclusion?
 
B. Assuming we were to decide that in a dry halakhic sense the parchment is invalid and should be replaced with different parchment, is there room to rely on the custom that the entire Jewish people follow, even though it has only a narrow basis? Would the answer change if we assume that Rabbeinu Tam would have retracted his view?
 
C. Even if we say that the custom is valid from the outset, would there still be an advantage to being stringent like the other medieval authorities (Rishonim), or is there a problem with deviating from the custom (casting aspersions on the earlier authorities, religious pretentiousness, and the like)?
 
Thank you very much in advance.