That's a nice trot! 4th pic is the best. If you compare it to the first pic, you'll see in pic 1 that your shoulders are rounded and your elbows are not resting at your sides. In that 4th pic, it's all there. Your shoulders are a little rounded, but not nearly as much as in pic 1. Your elbows are resting gently at your sides. Your horse is tracking up and using himself very well. Looks great.
For your upper body, just think about opening your shoulders. Overdo it at first by trying to touch your shouldblades together and then letting them slip back to neutral. Rotating your shoulders back and shoulder shrugs work well too as well as keep everything relaxed. Get those shoulders open and it will improve your position a lot. Beautiful horse. What breed is he?
You just have to see your distance...you don't have to like it.