You need to reboot your tablet and post the messages from the first time you run the chroot. You'll notice that your posted messages say, "chroot set up already!" so it is completely skipping the partition mounting steps. If it still says "chroot set up already!" after rebooting, you've messed something up in your script so that it never mounts the partition.

I run my chroot from a partition, too, because it is much faster, and all I did was change the ~/.chroot file to point to the right place.

Perhaps I should upload a tarball with the rootfs from the img file, so you can just untar that into your partition.