1. Is it possible to have more than one page tab
JFBConnect only support one Application ID. For that specific Application ID's Page Tab, JFBConnect gives you the ability to switch the Joomla template that is applied when viewed.
However, you can create as many Facebook Applications as you want and set their Page Tabs to different URLs on your site. You'll simply lose the ability to apply a custom template to these additional Page Tabs. JFBConnect won't be aware of them at all, but they will work as Page Tabs, just like you'd expect.
2. Is it possible to have more that one canvas
This is the same as above. You can have many Applications point their Canvas URL to different paths on your site. It shouldn't cause any problems if you do.
I hope that helps, but if you have any questions, just let me know.
Thanks,
Alex