a) Use debian.sh script instead of chrooting manually. It does whole /etc/resolv.conf, /dev, /sys etc. handling for you
b) Seems like you forgot to do "dpkg --configure -a" after first chrooting into Debian. multistrap instructions should say that
After that, I suggest "apt-get install dialog" and "dpkg-reconfigure locales" in order to select locales to build.