I got the keys I programmed as "Backspace" and "Escape" to work by using the attached "keyboard.xml" file that someone had posted at the XBMC forums. Well, not perfectly as both keys do backspace but it is good enough. The Flirc controlled remote even works for navigating around the Android OS with the arrow keys and the enter and exit keys. Pretty sweet setup now.
Edit: oh yeah, with the above "keyboard.xml" file the Rii mini keyboard keys (Escape, backspace, and shift) still don't work within XBMC but the Flirc remote does.
keyboard.xml