I read about this method of changing key mappings of your keyboard layout in the /usr/share/X11/xkb/symbols/ directory. I think this is basically what you do. In these files there are only symbols and “partial alphanumeric_keys” defined. I don’t see how keys like backspace can be redefined there. But I will look further into it.

Better ditch this crap and use AWK for manipulating tables. It has all the intelligence you’ll need.