your gettin up pretty good.. So.. what I know about balancing in the bowstall is the same to what Pishk was talking about. I can't balance for longer than 3 seconds myself but I'm getting better..
When you lift your head and chest higher and extend your back it pushes your feet down, causing you to fall over as you did in your video. when you put your head closer the water, it pulls your feet closer to you, causing your bow to come up.
So what does this mean to you as your balancing..
First, you want to have your paddle a little further away from your boat when you've finished your double pump, to make a "triangle" between your bow, head and paddle blades. . As you initiate next time, try going into it with your chest out, flexing your stomach and lower back a little. This will engage your hip flexors and give you better control of the bow as it sinks... Keep practicing your double pump so that you learn where you are more balanced once your vertical.
Now, when you're in your bow stall or going into it, pick a point in front of you, whether it's a beach, or pool side, or hot chick, to focus on. if you feel your bow surfacing, than look up a little more, if you feel your bow diving and your gonna fall face first, stretch out your arms, push them down more, and look down, face in the water.. the key is to pick a point in front of you and look at it, extend your arms out and have them a little further away from the boat than you do in the video.. GOOD LUCK