I don't have a 360, but I still suspect I can answer your questions.
1: It would likely depend on how many players the game is set up to handle locally, which is probably rarely going to exceed 4.
2: No, but you could get a cheap switch/hub and an extra cable or two to avoid having to swap the connection all the time.
1. So how many can play Multiplayer on xbox is it 16 max?
2. How do you hook up the 360...unplug my ethernet from my pc and into 360 then back to my pc for internet.does xbox have dual ethernet ports?