Are you the the GM for the game, or just one of the players. At this point, it appears to me that this player will be a negative influence on the game. He has all the hallmarks of a player that enjoys messing with the other players and doing his own thing rather than enjoying the campaign itself. If you are the GM, I would frankly inform him that his character concept will be far too disruptive to the campaign, and he needs to modify it. Specifically, the two real dealbreakers in question to me can be fixed if the character learns Common and the player just accepts that his character will not feed others human meat; any attempt to do so will simply be ignored by GM fiat. Also warn him that putting the other PCs to sleep may earn his character's rear a beat-down once they wake up, and if he kills them, then by GM fiat it will not have happened and he is out of the group.
If you are not the GM, but most or all of the other players are in agreement with you, then it's time for you all to bring your concerns to the GM. After the game starts will be too late, and will just cause more problems. It's best to deal with it now and get the drama over with before it messes up the campaign once you're into it.
Sadly, not every player wants to have fun as part of a group; some just want to do their own thing, regardless of how many other players they ruin it for. Maybe him getting called out will make him rethink his choices, maybe not, but better to know now than later.
Good luck.