+1.
My youth orch just played a side-by-side concert with the Houston Symphony playing Beethoven 5, so I learned a lot about this excerpt and stroke from the HSO bass section. I notice in the video, you play the 8ths fairly close to the frog and on the string. I might move a little further to the balance point of the bow, you can get some more bounce, but still keep a strong articulation. This stroke is definately off the string. Seeing the HSO bassists play this one, their bows are really flying off the string. I also had a couple coversations with David Malone, HSO acting principle bassist, about the articulations of the notes in this excerpt, and he said that the quarter notes of this excerpt should be played off the string as well. Hope this helps.
Ehh..this is all very tempo dependent. Tbh, I've never been taught that the quarters in the trio are to be played off the string. Makes no sense to me. If they were, it would be a brushed stroke, so much that it seems like the ratio between time spent on the string would make a lifted legato/detache more applicable. AFAIK most people play this excerpt on the string, with the stick bouncing, but I could be wrong. Might be some division in the bass world, and also orchestra dependent, but to say it's firmly one way or the other is surely incorrect.