Well, i got it to work, but I am not confident that my methodology was very secure.
I ran smtpd with strace debugging turned on and saw the reason that things weren't working was that postfix was searching for my saslauthd file in /var/run/saslauthd. The only mention of the /var/run directory i saw was in the saslauthd init.d file, which i changed to reflect the /var/spool/postfix/var/run/saslauthd directory. That didn't work, so I ended up copying and linking all the files necessary from the /spool directory into the /var/run/saslauthd directory. I can't imagine this is terribly secure?
Where is postfix pulling this /var/run directory from, anyway? If i can change that, I'd rather delete what I've done and do it the correct way.