Hey there! From what i have seen in your video, i can only agree with the other riders:
You are not leaning forward enough, and thats why the back end comes down so soon.
I know im not much of a talent in this sport, as i started learning this thing aswell (like 2 months ago), and still i started riding flat 6 years ago :S. After i got used to it, i figured out that its nearly the same as i got into a hang 5 (only need to counter-balance the frame if you want to travel without puting the back end down as soon as the frame turn around 180 degrees).
The steps to it i belive are:
1.: Start out with your left foot on the front left peg, and your right foot on the back left peg.
2.: Lean the bike to your right a bit.
3.: Now comes the big part: Push your bars forward. When you do that, the back wheel is about to leave the ground.
4.: As soon as you feel the back end coming up, you need to push the end of the bike with your right foot just a little bit to the right (if the bike is leaning to the right as described earlier, the frame should start spinning around easily).
5.: From this point, its up to you to counter the weight of your bike's back end with using your right foot, and a little more work on the bars with your arms to balance.
6.: If its enough for you, you can let the back end drop when it traveled around 180 degrees. From this point, you need to get comfortable with rolling in this position. After all this, its up to you how you continue, there are alot of ways.
This trick requires alot of dedication, and to eliminate the fear of you bailing out of it badly. While most tricks are a bit frightening at first, all that you fear of will disappear once you get that trick down for the first time!
I have some footage of what i belive you would be interested in. The difference is that when i do this, i don't let the back end down when it travels halfway, i try to counter the movement till the end changes direction, and comes back to the beginning pose. Here is the vid (the actual thing is from 3min 29sec, with some failed attempts cut together, and landing 4 at the end):
Hope i could help you with this, Good luck with the upcoming tricks! Keep on riding dude!