Hi Peter,
I think these are tougher than they need to be because you are not starting it off the floor with knee extension. In the deadlift, we extend knees and hips, and it should start off the floor with knee extension. Hips will extend soon enough. This is also likely the reason the barbell is drifting off your skin. Rep 1 was the best, but as the set goes on you are neglecting to extend your knees. Watch the angle your tibia makes with your femur. It should change within the first 6 inches of the pull, but it isn't.
So, get yourself set, deep breath, chest up hard, and push the floor away.