Calibre does not work via iTunes and USB. Apple does not allow third party applciations to connect via USB.
For over the network settings for some reason I found I had more joy using port 8787 on my Windows box. Note that you have to have your firewall configured to allow Calibre to act as a server on whatever port you select for use. You might prefer to start with the firewall turned off to prove everything is working and then you can enable it afterwards once it is correctly configured.
Also note that the URL to use depends on whether you are configuring Stanza to use a web page or an user defined catalog. The online catalog feature would use the address:
http://(IP number):8080/stanza
This is the best way to access the Calibre catalog from Stanza.