If anyone is still interested in this, I've published a writeup on my blog at
http://www.blit.ca/blog/fdey966ldd/Sic__Yet_Another_Mediocre_Small_Lisp_Dialect.html
The code is at
https://github.com/suetanvil/sic
(Pings to @rain and @ekaitz_zarraga who had expressed curiosity earlier.)