They probably have a way of knowing you watch porn by viewing what is going on with the network, but since almost everyone watches porn, who cares? I think it would be odd for there to be a rule against porn, but I suppose you could read the fine print of your lease? I know that when I watch porn while staying in hotel rooms and use the hotel wifi that the bored front desk staff can figure out who's watching porn because one time a lady at the front desk made a snide remark about "all that naughty video streaming" that was being done from my room.
Depends on how your connection is setup. Do you know if you are behind a proxy server? It is easy to check...just Google "How to check for Proxy Server for [what browser you use, IE or Firefox or Chrome] If you are on a dorm proxy then absolutely they will know, but I doubt you are on a proxy. If not...then it is highly unlikely.
im sure they could know if they wanted to .. but would they really want to. What would motivate them to attempt to track down someone watching porn (as if you're the only one)? if you're paranoid use a VPN then they won't be able to know but the people that operate the VPN service could know. they may say they keep no logs, .. but they could if they wanted to. I'm not sure how they would know that "it was you" though ... they would be able to see the HTTP headers but it could have been any other person connected to the network. If they can tell with certainty who you specifically are by by looking at some HTTP headers then you're probably doing more wrong than looking at porn and should reconsider what information you submit over the internet in the clear (without SSL/TLS crypto etc). You know, it's like saying "hey, who's 127.0.0.1?" ...