Agree with what's been said so far. Lifting your head and rolling your shoulders back will bring your arms and hands into a better frame by default. Its a habit I get into also: you get so into the horse, your upper body starts to collapse in. Get in a habit of constantly checking this in your head while you ride.
Your horse is looking good, pic number 3 is very encouraging:) Work on really getting him to reach under himself in the trot, he's not really using himself in that gait yet.