Ian
My recommendations. You should be at 15 off if not already there. Then get into one handed full time. It rally is more about confidence than anything, but it will definitely change the way you ski. It can be very useful in controlling slack. Two handed skiing encourages riding on your tail because it is hard to reach in to take up the slack. Then you end up pulling the hands in high - up by the chest, per your photo. With your back arm connected to the handle at the apex of the turn it forces your upper body to turn down course too soon.

Get some good slalom videos - and look into coaching. A little coaching at the beginning can save you decades of bad habits. Take it from someon trying to break 30 years of bad habits....