It is possible that you lost the executable bit thru the copying process when you copy from the USB Stick to the HDD1.
This might have resolved your first issue; I don't know.
chmod +x /tmp/hdd/volumes/HDD1/mediatomb/mediatomb.sh
You can not just take any DB file and use them with mediatomb I believe that the data structure is somewhat different amongst some of the various version of mediatomb. You should try to create a local feed from the disk or the example I gave in a previous post using the web interface and see if it works. If that works then you know that it's a DB version issue.