Mac Terminal support for multiple fonts
I don't think it'll be possible - terminal-based applications (as those running in terminal emulators like Terminal.app, iTerm.app, etc are) don't support multiple concurrent fonts. This is because a terminal application is written to run on a traditional dumb terminal which wouldn't have the concept of multiple fonts. Within a terminal emulator, all text is displayed in the same font and this is why the sidebar doesn't look as it should.

The only solution is to use a version of Emacs running under either Cocoa/Carbon (eg, Emacs.app or Aquamacs) or X11.