So, in conclusion, sex does exist, and there are about 7 billion people for whom the normal two sexes is an adequate description.

How on earth do you get from this to "sex doesn't exist"?

Gender is a different issue, but you document yourself that not only does it exist, but it's the absolutely overwhelming majority.

(You're only considering chromosomal sex; if you switch to morphological sex, you find that some of the above variants are basically morphologically male or female, but you also find that rare genetic variations exist that result in abnormal development of sex-specific tissues...but the numbers are similarly minuscule.)