Siblings are an easy target for stored up anger, and it can seem like you do one little thing, or even nothing at all, and suddenly get blown up at. Don't take his insults to heart.
Sometime when he's not in a bad mood, tell him that it bothers you and really hurts your feelings when he does things like that and calls you names. Ask him if he could just try to be a little more considerate of your feelings, and that if he needs to talk about something you will be right there to listen, and you'd like to help him if you can. Maybe once you two can get past the screaming, you can actually talk and figure out why he is getting in so much trouble, and what's going on in his life that makes him so angry.
But he might not be willing to accept any help at the moment, or to show that he cares about anything, so you'll just have to take it in stride and be there for him in case he does decide to talk to you about stuff.
Also, you may want to talk to your parents - tell them that the atmosphere in the house is making you nuts. Maybe they don't realize how out of hand it's gotten. Parents are often so focused on solving one problem - your brother's behavior in this case - that they don't realize that they have created another one. It always helps to talk about these things - at a time when everything is calm.
If it ever gets to the point where all the screaming going on in your household is making you feel like you are losing your grip, and you can't take it, there are lots of things you can do. Take a walk. Go in your room and turn your music up to where you can't here their arguing. Go to the library and get your homework done. Go to a friends house. Call up a friend and tell her that you just can't take it at your house right now and ask if you can come over for a couple hours.
Know that you are a good person, and that others in your house are going through a rough time right now, and probably aren't thinking how their words affect you.