Q2 looks very good. For Q3 you will have to make some kind of assumption about grade distribution.
The assumptions for grade distribution vary on the course offering, past history and other factors that can affect the distribution of grades. For example a course in Quantum ChromoDynamics will have a distribution that is a lot different to say a course in introductory economics.
When you figure out the assumptions to get the expected distribution or just obtain the expected distribution (through some argument) then you can do the chi-square test and obtain a test-statistic to test your hypothesis.
I don't think a uniform grade would a good assumption, but perhaps a Normally distributed grade curve or a skewed normal (like a Beta distribution) can be used.
If these are used then you will need to "bin" the distribution by dividing it into 6 even regions and get the probability (or rather the frequency) for each region where frequency is calculated by using frequency = probability * Number_Of_Students.