There seems to be an easy solution as it seems to me.
1)
He will need about 2 hours to watch a 1 hour video. That is if he watches high quality videos for 6 hours a day, he will need about 12 of download time. If you have 2mb/s connection.
All of it and more can be downloaded at sleep time + school/university time.
So, worst case scenario, the problem is solved.
2)
when he wants to do something on demand (download HD clips,) he can always leave you like 30-60KB/s. It shouldn't be a big deal for him, but it can ensure you comfortable web browsing. (web browsing is not like downloading, it takes much less bandwidth.)
That's how I solve the problem with myself! At night, I download all I want and more. And when I want to browse at night, I leave like 200KB/s for download, and 40KB/s for browsing.
What browsing speed do you have by the way?