Correct me if I'm wrong, but isn't it correct to say that there are two genders, but not that there are two sexes? Since gender is only a social construct, presumably the prevailing views of the society in question are what defines it?
I'd add a couple more things to condition your list:
* people are sometimes contextually gendered or contextually express specific sexuality (I know people who might describe themselves - and present that way too - as TV in some situations, but not others. I might imagine certain contextuality in sex is possible also, but with rather more logistical difficulty
* people sometimes change over time, and while they may choose to simply identify as their current (or desired goal situation) sex/gender/sexuality/... some people are happy to identify some or all aspects of their history, such as visible trans people
It's a pretty diverse world out there if you pay attention, even in somewhat conservative communities, so take care out there.
Not really. Who gets to decide what the prevailing views of the society are? For that matter, which society? A non-binary construction of gender is not limited to post-industrial cities in the United States.