Hi Jamil,
I'm afraid I don't really have answers to your questions, but we do see similar problems for customers who are using Totara for many years now. So I hope to see some answers here that can help us as well.
If any tips could be shared how to clean up on the server side, that would also work for us.
I do know that customers that use a lot of video's often combine a Vimeo account with Totara, because that is made to store video's and easily linked and secure. But that doesn't help your full server now..
Kind regards,
Irma