a big reason that drove me was that I have a micropenis
Fake. There are no "reasons to drive someone" other than their internal gender, this sounds like something a cis person who thinks being trans is a choice would say.
Edit: I'm not speculation on OOPs gender
Yeah, certainly seems fake. But I can conceive of someone that's NB, fluid, or something else who is unable/unwilling to admit that to themselves or choosing to remain cis presenting for social reasons deciding to present as a woman due to a micropenis.
But yeah, fake.
whilst this is what being transgender 'is', that doesn't stop idiots from socially or medically transitioning for poor reasons.
There isn't any evidence that that happens (non trans people receiving gender affirming care based on a false view that they are trans)
You should use she/her pronouns given we know they were AMAB and are trans. At the very least they/them. He/him is almost certainly wrong.