Of course they can be chosen. They aren't handed down from God.
So tell me - when did you choose your pronoun and why did you choose the one that you chose?
Right or wrong based on what? Sex? Not according to you. Gender? Maybe, except you said that's not distinct from sex.
Let's assume for the moment that pronouns are determined by sex. And that by "sex" we mean biological characteristics - basically, what genitals someone has. Because that's all "sex" means in this context. How do you know what genitals someone has? Are you asking them? Sneaking a peek? Demanding that they show them to you so you can know what pronouns to use? Okay, so let's de-creepify this scenario and say that instead of genitals we're concerned with chromosomes. How do you know that a particular person has XY chromosomes? You don't. You can't.
So pronouns
can't possibly be determined by sex, because you fundamentally
cannot know what sex someone is without either them telling you or you being a complete creep.
If you go by vague general appearance and take a stab based on that, as I said, you'll be right 90% of the time. If you do this, and the person you are referring to happens to be passing transgender, then you've used correct pronoun anyway. Win-win.
Irrelevant. Doesn't even have to be completely bespoke. Even "they/them" works for what I was trying to say, and it's actually what I almost wrote there.
No, because you already use they/them in your normal speech. Everybody does. That's why it's used instead of new invented words.
What in Lucifer's good name is my cue that some guy I see at the smoking place twice a week, and once in a meeting, and I don't care enough about to even remember the name of, is neither a he nor a she?
I've told you five times now that nobody expects you to do that.
Besides, I have actually heard (well, read) more than one use shi/hir before in a chat room. That's why I've said I've only heard it used by trans furries before. Because I actually have. And asked what it meant. And it was in 2000 or 2001 or so, long before the current pronouns carnival. So, not quite that infinitesimal.
Once, in your lifetime, twenty five years ago, in a very niche community.
Like I said, infinitesimal.