Need to reassign all the assignments for every new student, can't assign SAT skills, and can't change all the due dates

I tried using Khan Academy for an SAT class this spring but ran into 3 issues:
1. Every time a kid joins my class, I have to reassign them everything. Can I set it so all new students automatically get what I assigned the rest of the class?
2. I'm trying to assign SAT skills, but get the error message "Teachers cannot currently assign SAT skill practice or practice tests to their students." What good is Khan Academy if we can't assign them SAT skill practice? Can I override this?
3. I'm trying to extend the due dates for everything, but when I go to "Manage Assignments" and click the top box to check every box, the only option is to delete everything. The only way I can change a due date is to change each one individually which takes hours when you have a lot assigned.