Wow I missed something! I have been reading your post looking at your picture and totally thought you were already transitioned. You look like it and you sound like it and I think that means its time for you.
Never the less as I have said before this is like one of the most difficult parts of transitioning is how to handle your workplace transition and not loose your job!!!! I know for a fact (somehow) you would have been transitioned long ago if this wasn't for this obstacle. I can feel your pain, it must be terrible.
You know you have to do something so why not make your first try something you can get out of if you get a negative response. I suggest that you do talk to your boss he sounds nice and most likely already has a clue that your are a bit feminine. But you do it in a way that is between you and him with zero demands. Come out to him ask does he think it would ever be possible for you transition at work and if the answer is no then tell him you wont but thank you for listening and you really like your job (smooth it out) and start looking for a new way. If he says OK well then your in and there you go girl.
I know were your at Ive been just there and I did just what I suggested to you right now and they said YES.
What do you think maybe you can do that ? Hey if your pushing the envelope in that way already! Your gonna out yourself in a uncontrolled fashion and I say take control and test the waters in a way that makes more sense.
Very Sincerely
Kristina