I agree with all except the advice to lower and spread your hands. It might be trendy in HUS shows, but is not the correct position to have your hands, except in some instances when working on particulr problems. I think the height of your hands was about right for maintaining that line of elbow to bit, through the hand. YOu need to strictly keep your thumbes on top, make a bit more contact with the rein/mouth and get the hrose to have a bit of flex to the inside, just a little, so that he will be giving you a more consistant contact with your outside rein.
Your seat is lovely, quiet leg, upright stance, very well balanced and sympathetic to your horse. I think if you had been able to get a little more committment of forward energy from that horse, you would have taken first!