Answers to your questions:
1. Yes, it's ok to change the admin user/pass in the .xml file to your preferred one . but it can't be done within the browser, please modify fcserver.xml and restart the chat server to see it take effect.
2. you can set password-protected rooms to users in our new version this weekend. then "Only Math student sget to enter the Math room".
about "subdivide into group rooms", that need you start multi-chat-servers on your server.
3. About voice and video, maybe in 1 or 2 months. :
