KiNdReD

I thought that these were a couple of the best lines of the novel:
"She means it doesn't come off, Dana. The black. She means the devil with people who say you're anything but what you are."
I first viewed this quote in a positive way, considering the context of the black slaves accusing Dana of being "too white," and almost betraying them. But, after reading it a few times, I get the feeling that maybe Butler used this line to say that black people couldn't escape the oppressions that came along with having black skin, no matter how educated they were, or what century they came from. Butler applies the same idea in 1976 when Kevin's sister absolutely rejected Dana and wanted nothing to do with her. She uses this scenario to explain to the reader that although the racism and oppression is not nearly as horrifying or degrading as it used to be, it still was present in 1976 and even today.
When I was reading the novel, I was wondering if there was any deeper meaning to Dana always wearing pants and dressing as a "man" because it was brought up constantly. Did people respect her more just by simply being dressed like a man? She had several opportunities to change the way she dressed, but she always opted not to. Maybe I am reading into this too much, but I was just wondering what other people thought about it.
Also, I was very VERY confused as to what exactly happened at the end of the novel with Dana's arm and the wall. Why did that happen? If someone could please explain that to me I woud be very much appreciative.