QuoteWhat is innate about gender?
Nothing.
The OED defines gender as

Using the word the way we do here is following in the footsteps of 1960s feminism.
QuoteWhy when I don't believe in gender and black and white this side and that do I still feel transgender and have dysphoric feelings about pronouns?
Because "he" and "she" act as unambiguous sexual markers. Since there is a dissonance with how you feel ("No, that's wrong!"), the language processing parts of your brain will fire at parts of your brain responsible for sending back signals such as disgust, rage, and sadness.
QuoteWhy do I want to be a straight woman when I don't hate my penis (I'm terrified of that surgery.)
That's okay. I don't hate mine, either. Not crazy about it, but until they can give me a functional uterus so guys can make babies with me, I'm not sold on the idea of some ersatz vulva. Even then, I'd rather have an axlotl tank. ;-)
QuoteWhy can't I be fine with who I am?
The way I see it, gender roles are examples of conditioning, whereas gender identity preferences are examples of imprinting.
When we break our conditioning, we re-program our brains to activate synapses that align with the previously imprinted identity pattern.
So far, that seems logical. The misalignment causes increased cognitive load. Since reversing imprinting is disproportionally more difficult, re-conditioning makes more sense.
You can re-program yourself into whatever you want. The only limitations are those that you allow other people to impose on you.