your shoulder, hip , ankle alingment is getting really good. As you said, you do need to work on having your hands with thumbs on top. Paramount to doing that is having your elbow in to your side. It's all about bringing your strength to the core of your being, and when your elbows are out, your hands rotate downward , you look down through the openning formed by your elbows "winging" out, and your energy goes forward and literally encourages the horse to be strung out on the forehand.
This horse has a ewe neck and is obviously used to moving with it's head in the air and on the forehand. The more centered you can get (and your alignment is good and a good start), the more encouraged the horse is to become centered, himself.
When he raises his head, dont' try to pull him down by lowering your hands. Instead, follow him up, your elbows in, maintinaing a straight line connection to his mouth, and keep gently asking him to soften to the bit. When he does, even a little, give him a big release on the rein, and maybe a one handed pat on the neck and let him walk forward on a looser rein. Eventually, you will follow him up (if he "giraffes"), ask him to soften and flex at the poll, give a tiny release with your hands, ask him to step forward but NOT give away the contact totally and you will have him stepping into the bit without giraffing.
Little by little , you build on that