Yes, they know how much you need to learn in this school year and they way that against how much the class is actually getting the material in class. So, if everyone participates in class and is really paying attention, homework is usually less.
Yes. Homework should be based on how well your class "gets" the lessons during the school day. If your class is having difficulty with a particular subject, homework is usually assigned since you need more practice.
Yes. I found my hardest teachers to be the best teachers. Giving you a lot of homework now will prepare you for college. If it's truly an insane amount of homework have your classmates all tell your parents. Your parents can then discuss it at patent teacher night.