Hi and and warm welcome to the forums!
Is it possible to delete your facebook and do a fresh restart if you want? I had to delete mine a few years back but I never got back on it (and no regrets).
As for the photos and videos that's a personal decision. Personally I'd probably delete as much as possible and then when I'm worn out take a break and restart when I'm up for it.
I'm sorry you had a manic episode. I hope your future is much kinder to you