Thanks, all. It looks like the opinions here are split 50/50, but that's fairly representative of my feelings on the matter. *shrug*
Yeah, I plan to live on campus. And I am out to my mom. She doesn't quite understand, but she supports me, to an extent. Her feelings are that transmen take something away from the dyke community when they decide to transition and "get male privilege," but I've observed that these days, there's much less division in the GLBT youth community between lesbians, gays, queers, transfolk (at least in my school) and I told her such. So... a little progress, maybe.
The problem is, I moved in with Mom and her girlfriend when I was eight, and immediately the girlfriend started correcting my masculine behavior. I have to accept that this is all about her, because she has an incredibly inflated opinion of her own ability to influence me, and I think she imagines that her wearing boxer briefs "caused" me to act masculine.

So basically, I took her corrections. And because of that, it's not intuitive to me to act the way I'm supposed to. I feel like I lost all the years of my life that I've had since I was eight, in a sense, because I didn't fight back. Because I was raised
wrong. Point of that whole self-pitying monologue is, it takes a lot of extra effort to make her believe that she's been successful, especially since recently it's been getting a lot more difficult to present the way she wants me to. I see it as a balance between how masculine I allow myself to behave, and how vociferous I am in reassuring her that "I'm not trans."
So - I do understand the value of fighting back. It makes me feel like crap to have to act like such a sissy, and it makes me feel like worse crap to say this stuff about my closest friends, which is why I'm not gonna anymore. But I think the kind of fight I have to take on, here, is more... subtle, I guess, than forcing her to become accepting of every choice I make and to discard every illusion she has about trans folk.
I'm beginning to transition socially with my friends, and I'm going to buy a binder as soon as I get the chance, to wear to school. You know - little stuff. The things that change how I see myself, not necessarily how she sees me. I figure drag queens manage to act like a gender they're not, in a certain space - but as soon as they're out of that space, they're men again. And on the inside, they always were. So if that works for them - and if that's what it takes to not have to talk ->-bleeped-<- about my friends - then that's what I'll do.