“ujm, we have apparently one case of mass execution by Shimon b’ Shetach in history (who lived in generally very bloody and desperate times) v. opinions in Makkos that executing one person in 70 years makes a bloody court. So, how do we weigh inappropriate dresses v. other problems Sanhedrin will be dealing with – say, murderers, informers, communists, idol worshippers, pandemic rule breakers?“
I had the same question and I think that גמרא that says it’s a בית דין של רוצחים is because part of their job is prevention through teaching and if someone is חייב מיתה it’s because they didn’t teach it is wrong properly
This applies to everything you mentioned