Noticed this while looking through threads while logged out and felt the need to put my two cents in. I’m not going to promise my thoughts aren’t going to be offensive.
As far as I’m concerned, this is your main problem. You’re treating sex and gender (and no, gender role does not equal gender) as if they are the same, they aren’t. If you’re going to add an option for gender-fluidity, I’d ask the player if their character is male, female, or intersex before asking for their gender if you want to keep things simple or:
If you don’t mind the extra work.
For the love of the gods do not treat gender-fluid PCs as if they’re non-binary trans PCs. At the very least treat them the same way you’d treat bi-gender/tri-gender/etc. trans PC, as in, give them the ability to change their pronouns whenever they want. While some gender-fluid people might not care, others probably will.
Finally, read every answer here. If you have any specific questions for me afterwards, feel free to ask and keep in mind that I only speak for myself.