Oh darling, the thing is dickheads are everywhere and if you are not the boss then there's nothing you can do. Because mostly, they are part of the boss' family or maybe distant family or -and I think this is the most plausible because I saw it several times in other situations- these dickheads know something about that boss, could be something related to the job or maybe they go for drinks and while drunk this boss does something shameful or unfaithful -if you know what I mean. So, if as you said you have complained in several ways to your boss and maybe your other collegues have done it as well, then it's likely that nothing will happen to this oxigen-robber. Someone must be backing him in a way and this someone must have power over your boss. It's really sad but as far as I can tell from your post, this guy is doing things wrong more frequently than before and even your boss is getting notice of it. So, let him dig himself a very deep grave because those consequences will be awful and what is better is that it will be brought by himself. Be careful as to not present yourself as the one fighting on the office since he is likely to be backed from above. Do it after other collegues. Also, if you can have a private conversation along with your collegues, I mean a groupal discussion about what they think of the situation so you all can show a united front to face this undesired being when the time comes for him to fall to his grave or if he tries to blame any of you. Hope I can help with these humble ideas, I know is not easy. Have a bright day!