[hga]

WRT 3, assoc lists are just the simplest thing to store things like environments, they're traditional for "writing a Lisp in one week". If you modulerize your code, you can trivially use hash tables or whatever later. Ditto using lists for structures.

4: As I understand it, there are many macro systems available for Scheme. It's one of the languages in which "hygienic" macros has been explored, etc. So if you don't like the femtolisp bundled version, there might be another out there more to your taste.