Ummm... outside of the partying (against house rules) you jump to " I believe a porno might be being made given the odd amount of men - women ratio at my property"? I wouldn't jump to that decision and it's an accusation that will immeidately make AirBnB less than happy to help - because you are showing yourself highly suseptible to jumping to conclusions. I would avoid words like "Staking out" etc.
Just call AirBnB, tell them the BASICS... "broke house rules" "had party" "guests OTHER than registered guests on the property" I am no longer comfortable renting to these people. Can you (AirBnB) cancel this reservation so I as host am not "dinged" for it - or find them alternative accomodations?