People tend to save their worst behavior for those with whom they feel comfortable. Clearly, he’s totally comfortable with you. And I agree, he is probably depressed. Go to the RA, ask to be moved to another room. Explain that you are also concerned about his well-being, but that you cannot live in the dark, and that you are letting the RA know that in addition to this being a roommate issue, it’s probably a mental health issue for him, and that he needs someone to check in on him. From what you describe, it sounds as if he has stopped going to classes. BTW, are your parents friends with his parents? If this were happening with my son, I would want to know about it. If you guys have been friends since elementary school, I bet your parents know each other, and if you say something to your parent, they would probably let his parent know he’s having problems.
Meanwhile, get a couple of gooseneck directional lamps for your side of the room, directed onto your desk, and towards your bed. When you are in the room, and it’s not sleeping time, use them as you see fit. If he turns them off, tell him in no uncertain terms that you need the light on to read and study and see. Tell him that you find having the blinds closed during the day depressing, and that you want them open during the day. If he starts insulting you, tell him to cut it out, and if he continues, go back to the RA and tell him to expedite the move. You should not have to live with abuse.