1) I don't think this is a big problem myself, I work on both 800x600, 1024x768 and 1600x1200, systems. And to me it seems to work right. I don't think it will be easy trying to fit everything in a theme with a width of 750.
But it's atleast worth looking into (but not toooo soon

).
2) It is a bit hard to implement this, (well not really, but in a clean way it is). What I suggested to ztonzy (who asked me this aswell) is simply to change the css, so that the browsers can change the fonts. (I know opera, and mozilla atleast do this already, and IE 6.0 can do it as soon as I change the css tags).
I will decide a bit more about the development process of blender.org next week. (will e-mail you about this aswell).
Greets,
Timothy