Glad you're enjoying the game! If you click the Rename/Options button in the Sanctum you can change the protagonist's pronouns, though there's no support for they/them.
Petite cock should live in the Tome of Genital Swapping, though it looks like there's a bug where you can't go back to it from larger cocks. As a workaround you could get a strap-on, then get a petite cock. In general there shouldn't be anything irreversible in there, and if there is, I appreciate the bug reports. Cheers!