You have quite a situation and I would like to respond further when I am able but I am short on time now.

The combination of sedatives and alcohol can be deadly. He may well need sedatives but he needs to get those prescribed for him and he should take them as prescribed. Alcohol is a depressant and though it might feel good for the moment no good can come of using alcohol.

The college/univ should have therapists available and may have psychiatrists. Even if he has to pay he needs to see a professional and soon. If he is doing poorly in classes related to depression or a mental problem he may be able to get special consideration from the office of exceptional students; the therapist/doctor can help with this.