As chris said, this is an idiosyncratic puzzle, heavily themed on a subject I know nothing about. Likely will take a long time to solve.
Maybe best to simply read the postmortem coverage on 225.
8a was my FOI but not easy and took a lot of thought. Definition "mistake", a fun but not-so-common word. Parses as 4, 3, 1 where the 1 is indeed M. The 4 is "only", and the 3 is an abbreviation for "matching gender observed at birth" that I only became aware of in the past few years (gender politics and all that).