I've got as far as ...
Sure, about .2% of people have some sort of DSD.
And
As I demonstrate in my book Race, Monogamy, and Other Lies They Told You, brains are no more “sexed””^ at birth than are kidneys and livers. Rather, brains are “mosaics””^ of characteristically female and male features.
^^
Correct. The blue brain/pink brain notion is bollocks.
Of course, there are clear bodily differences in capacities to give birth and lactate, and ranges of patterns in the development and distribution of body size, strength, and myriad other processes. But such patterns are mostly overlapping, and only a few are distributed in clear or functional dichotomies.
True. But there are differences. The birth/lactation aren't minor issues (and are what gives rise to much structural sexism and enforced 'gender roles'. The distributions for size and strength are significantly displaced so that although the overlap means the can be women firefighters, it makes non segregated sports unfair and often unsafe.