You could also try live-booting Debian and see if it works out of the box.

It looks like you’re relying on media automounting to access the drive, but this is happening too late for Docker.

I would suggest creating the empty folder and explicitly adding the mount to /etc/fstab instead. This should mount early enough, and even if it doesn’t it needs an empty folder for the mount point anyway.

Edit: Make sure you reference the partition by UUID, because the device name of USB devices sometimes change after a reboot.