I see a reason to run ssh on the Zeroshell box. I really don’t see a reason to run the ssh subsystem sftp-server. You should only have to use the sftp client to move files to and from your zeroshell box.
I understand the need for backing up the /Database directory. I see the software you are wanting to use works with Samba, SSH, RSH, NFS and rsync. Rsync would be a better choice because it will only copy data that is changed and or new. Why backup the same data day after day if nothing has changed. or Why transfer the files that have not changed. Rsync can also transfer files via a rsync stream. I would be more supportive of rsync due to the features it provides.