For starters you are quoting US law. Copyright in Australia lasts 70 years after the person's death.Well he wrote it, composed it and it is definitely his non plagiarised ideas, so it is his intellectual property (until 50 years after he dies).
He can do whatever he wants with it.
Secondly, as a teacher anything I produce for school is automatically copyrighted to the department of education. It is one of our conditions of employment. Technically anything I produce for a class of mine can't be used for tutoring without the permission of the education department, and all such sheets can be used by any other teacher in the department in teaching their classes without seeking my permission.
In a similar vain, you and everyone who did the HSC signed a waiver to your IP rights. I'm not sure how far this goes, but you definitely can't distribute the PDF of the responses you were sent. I'm not sure whether it applies to typing up answers, but I would be modifying them considerably to be sure.