I think you either need to tell the landlord about him so he can send him a notice or find another place but still tell the landlord. The landlord has the right to know if the space is being ruined and filthy. He also needs to know this guy is violating other renters in the house - going in your bedroom is actually against the law IMO and completely creepy. Tell the landlord he did this and you can't stand the smell - let him know its either him or you. I don't think you can have peace of mind with him roaming around.