You given a nice wide variety of photos to critique.
photo #1 - heel up, rounded back, not enough release
photo #2 and #3 - can't really critique head on shots
photo #4 - best equitation shot of the bunch. Rock solid lower leg, right in the middle of your horse, lovely flat back, looking in the direction of your turn, but not exagerating it. Better release, still a little restrictive
photo #5 - still solid lower leg, right in the middle of the horse, but the roach in your back is back, which is interesting, as it's a lower, less intimidating fence than 4. Perhaps preparing for a turn makes you look up and lift your shoulder in the air?
photo #6 - not a shot I would have included, as it does not do you justice. Jumping ahead, pivoting on knee, laying on the horse's neck. This is a different horse than the other photos, correct?
The horse in the first 5 photos is *spectacular* and is overjumping everything by a foot and a half. Plenty of jump, plenty of scope, and I bet it's a challenge to stay with him. He looks like a seriously talented horse who is capable of doing lots more. However, I suspect some of the flaws in your eq are a direct result of riding this powerhouse. I suspect the rounded back occurs when you try to sit behind the motion going down to the fence and then attempt to catch up in the air; and I suspect the restrictive release is from, well, trying to restrict him! If you give a bigger release in the air, I'm guessing he's harder to bring back to you on the other side of the fence?
Overall, I think you're a talented, capable, athletic rider. If I had the privlege of having you and your lovely horse in my barn, I would put you on a bunch of other horses with different ways of going and jumping styles and work on your back and release. For your spectacular horse, I would stay up nights designing tricky gymnastics and exercises with placement rails so the fences and the exercise themselves would back him off, and teach him to jump a little more appropriately without relying on the rider to do so.
Best of luck to you!