My son lifted identically to you - i.e. the big pelvic thrust which shot the bar out in an arc.
We went to the catalyst dvd - snatch and went back to basics using just a bar and have been increasing the weight slowly up to where he was.
He wasnt rotating his elbows out at the start position. He also wasnt doing the snatch high pull with bent arms at the top and then transitioning under the bar and going down into the squat. He couldnt do that because of the arc outwards from the body after the pelvic thrust. He was doing the pelvic thrust as opposed to pulling the bar up and jumping up - explained better on the dvd.
So the snatches he missed were always in front cause that was where the bar was travelling after the pelvic thrust.
Doing it the way he was doing it meant that he had to plop the snatch right in the perfect spot - hence he was real hit and miss on the heavier snatches (70kg and above). He had previously been sprung by the judges for hitching as well. He was jumping backwards a far way too - you look to be going back about 2-3 inches as well which is better than him he was going back about 4-6 inches.
We have had the dvd for a couple of years (and in desperation/frustration) but I have to say the dvd really really helped.
The bar travel is now nearly in a straight line and we are just going heavy again.
The dvd breaks each of the pulls/moves down (special attention to the scarecrow). Get someone to video you and while your doing the moves.
He jumped from 80kg to a pb of 87kg the week after we started hammering his technique.
Like they say when in doubt read the instructions.