Matt - Good self assessment, like Greg says. My guess is that you'll be surprised how much of the problems will go away just by looking ahead and getting your chest up at the starting position. In your pull it doesn't look like the bar is anywhere close to you at any point, and keeping your chest up should help with that.
David D - My impression of the issue is that strength standing up won't be the limiting factor, how stable you are in the receiving position could be. Irrelevant of how strong your muscles are with an angled back, a vertical spine will still be more stable, allowing you to balance the bar overhead easier. If you can receive the bar with stability, I'd almost guarantee you'll be able to stand up with it.