When I read the first few lines of your post, I was afraid you were my daughter posting.
You are nineteen, and taking that leap and moving out is scary- but you won't be moving away never to return. You mention your dogs, chickens, etc...thats what visits are for. Get a friend, share the rent. Check out dorms at your school. School loans- do not have to be paid back until you have been out of school for six months and then it is in monthly payments. Parents will still help you, thats what we do- you can always go over there for dinner, etc., laundry., etc. You would be moving out of the house, not out of your life.
I am sorry that your brother is the way he is. It kills us as parents to have a child that will not take responsibility for his own life. I have a son who is a school drop out addict. He is seventeen. He is also bi-polar, and it kills me how he hates his sisters and me. Threatening your parents that you will do this or that or getting CPS involved does not help family dynamics. You are old enough to be on your own and away from the situation. Take your situation as a kick in the butt to do what millions of other eighteen year olds are doing- leaving home and going to college. Mac and cheese, ramen noodles, and bologna sandwiches and parents home for Sunday dinner are college staples. You will be okay.
You do not need to threaten your parents that if they don't kick him out, you are moving out. Make your decision to move out part of growing up. It will not help your parents to be threatened that you are moving- discuss it as an adult. Then do it. You don't have to move across the country, and you can still visit.