I'd say with the strange phone message telling him to be careful and the drugging of the drink points heavily towards him being the one who did it. Last time I played that part of the game I remember that we are forced to go with him but it's possible that was changed in the newer versions of the game. I admit that I've never invited him in the house so I have no idea how that plays out.
so on regards of the bathroom scene if you're character has enough dominance and choses to banish the cock then you will be met outside the bathroom by the 2 wolf's that would usually confront you but one will say he is going to get revenge conforming that is the person in the stall but it seemed you were saying that he tries taking advantage of viv before she goes in the bathroom not that the glory hole scene was him trying to take advantage of viv