@Kelli214 Of course I'm not the one faced with this guest, so don't know exactly what approach I'd take with him- he doesn't sound like someone who is easily approachable, but I might send him an Airbnb mesage (so it's documented for Airbnb to see, if necessary) something along the lines of "Hi XX, I'm pretty upset with the fact that you misrepresented the nature of your dog, telling me he was very friendly, when he is still growling and barking at others in the household after a week. You also assured me that the dog would be going everywhere with you, when this has proven not to be the case. I accepted you and your dog based on what you had told me, and because you have not followed through with your assurances, and left the dog alone in the room while you go out, I am wary about damage the dog may do or have done in there unsupervised. While I respect my guests' privacy, the fact that you have repeatedly disallowed me from entering the room to place fresh towels and do a quick clean leads me to feel you are trying to hide something. I am open to discussing this situation with you, but if you are not amenable to this, and continue to leave your dog alone here, it would be best if you look for another place to stay and cancel the remainder of your stay here, as I am quite uncomfortable with this state of affairs and it appears that you don't understand the need for mutual respect in a home-share."
If he doesn't answer, gets nasty about it, or insists on continuing his behavior, seems like the next step is to call Airbnb, explain the situation, asking them to look at your message stream with the guest, telling them he completely misrepresented the dog situation, that the dog is growling and barking at others in the household, which is completely unacceptable, and that you'd like them to cancel the rest of this guest's reservation with no penalties to you.
Or if the unfriendliness of the dog and the behavior of the guest is such that you are going to be stressed having him remain in your home altogether, which to me is a quite reasonable stance, skip the first approach and just ask Airbnb to cancel his booking. If he was just there for a week, it might not be worth doing, but having this situation in your home for a long-term reservation seems untenable to me.