I don't know how the laws work in Canada. What I can tell you is that IF you email specific detailed reports to HR no one there can claim that they didn't know. I'd blind CC all the emails to your personal email address as well, so you have a record.
If the harassment is ongoing that will likely make a difference to the complaint being heard in April, and documentation is crucial for that.
What are the realistic odds that everyone doesn't know now?
Remember, HR is NOT your friend. They are, however, important witnesses in any legal proceeding and they mostly know enough not to lie outright. PLUS it is their job to handle these kinds of things appropriately.
Remember at the same time, your manager is your boss, and you have to keep being a good employee and a good scout. When they suggest stuff to do, go ahead. It is an excellent opportunity to practice having good boundaries. With the manager, as much as you can (and I know this is like, THE ISSUE) try NOT to "bite the hook" and get pulled in.
Find out what your employers policies are on this stuff, when they don't follow them, put it in the record. Don't give them room to deny ANYTHING. Writing is power. And you are GOOD at writing.
And on the emotional side, it is just awful. Try try try to distract yourself when you start to "ruminate." I know. Been there, done that, got the T-shirt.:blackeye: