I'm similar myself, I don't dress very girly, I dress the way I want to, at times a dress, at times a skirt, but mostly jeans or baggy pants. At times my adorable womans winter coat that is amazing and everyone is jealous of, at times my bomberjacket.
I never tried, and probably never will try to be super girly. Like you said there are exceptions where you might get extra dressed up, and going to the Nobel Dinner in my bomberjacket might result in me getting throught out the door, or atleast not let in.

I have no real issues passing, at times I pass, at times I don't, I don't really care. But you don't have to be girly and very femme to pass, to me passing is how I feel more then how I dress. If I go out feeling like a woman (which I do), then it don't matter what I wear. Now that's not to say that you can wear anything and you'll pass if you "just believe in yourself, and the power of friendship!". But I personally belive that the most important part of passing is your view of yourself and how comfortable you are in yourself.
As for your hair I can't really comment much, it looks cute on you I find, but that's just one persons opinion. I got long hair myself and blooming hate it and thinking about cutting it off with a knife so that I have to go and sort it out at a hairdresses.

But as a transgirl who far from always dress girly and mostly pass (it's me bloody voice that gives me away most of the time.) I don't see anything wrong with wanting to be a tomboy. More power to you for questioning what "you're suppose to do"!