using the wrong name

As a background to this, I came out to my mom as transgender about a month ago but I'm sure she was suspecting it far prior to this. In the past year, she's been using (full gender-specific birth name (FGBN)) instead of (shortened non-gender-specific form of birth name (SN)) to refer to me far more often, and I do suspect she's been encouraging other family members to do the same based on what they have called me at family gatherings. I've preferred SN at least since I was in third grade ten years ago, and pretty much gotten called SN since then, even by teachers. The only thing I ever use FGBN for is Legal Stuff. Even when I'm ordering stuff online, I put SN as my billing address.
I've tried breaching this subject with Mom at a few different times, and she just says "Oh it's no big deal, it's your name." I want to tell her that yes, this is a big deal, and I would appreciate being called, if not Alison, at least SN. So this is the letter I'm going to send, and feedback would be very appreciated:


Hi Mom,
I told you I'm transgender on Thanksgiving Day, and I think you'd been suspecting it far prior to that. But ever since then, you've been calling me FGBN more and more. Maybe this is an unconscious response, maybe you're doing it on purpose, I don't know, but it really worries me that you won't be accepting of my transition. Could you please make an effort to call me, if not Alison, then SN, and raise the issue with family as well? I feel threatened when I'm referred to as FGBN because it forces me into a gender which I am not.

Thank you,
Alison


Also, do you have any advice in this situation? My dad was writing a letter to my nephew for his first birthday, and he asked me to proofread it because English isn't his first language. In the letter he used the word "gentleperson" and I was like, "Dad, I'd use 'gentleman' here because 'gentleperson' is a stilted neologism and sounds icky." To which Dad replied, in not these exact words, "I'm just leaving open the possibility that he be like you."
What is that supposed to mean? Does it mean that dad knows because mom told him, because I sure as hell didn't tell dad.

xposted to transgender