TCP 6690 port forward is only needed if you are going to have remote (off-the-LAN) desktop client devices connecting to Drive server. If you are not then you can remove it. Just one thought: if you do use desktop clients from the LAN then you will have to decide which server name/IP address you are going to use to access the NAS. With a secured connection it may throw an alert when setting up the client if the SSL certificate doesn't match that server name. See what happens and ask if you need help.