First of all, I would have you start with your vision fixed straight ahead before you lift the bar off the floor. This will help you keep your chest up a little better as you start the lift. Your back isn't hunched over but your chest is pointed down. Think about your hips and shoulders rising at the same time so your back angle stays the same.
During the first pull of the lift, the bar should be making an angle back toward your body. Your bar path is a little too vertical. Watch the 3rd video you posted ("23.01.2014 Snatch @ 50 + fail"). You can see a slight difference between the bar path of the 1st lift and the 2nd lift. In the first lift, the bar is too vertical leaving it too far out in front of you as you go into the second pull. In the 2nd lift, you'll see that you bring the bar back a little bit. Those little mistakes will make or break a lift.
Also, I notice that you are bending the elbow before you go into the 2nd pull. This will cause a big loss of power that is being produced with the legs. Keep the arms loose all the way through the extension and let the legs do the work.