Some good analysis in there and looks a little better. I wouldn't say the pros spin out, they pivot. Spin out is bad, that means there is a loss of resistance to torque against which results in a long slow spin of the foot typically. Pivot is a kinetic release of torque and is typically super fast and short. You are spot on about being uncoiled as late as possible in the x-step, I'm loose as a goose until my front foot begins striding forward past the rear foot and then my core loads down into the rear leg/hip as the upper body stays back(still in posture against the rear leg) with the front foot moving forward.
Moser does a different hop than others like Ulibarri used to where the rear leg never crosses behind, and they do a little two hop on the rear foot. You have to maintain good balance to do this type hop move or you will fail miserably. I'd also note Moser doesn't throw quite as far as the other top guys, but he putts and approaches lights out!
The Brinster, GG, Feldy type hop is what I've become most comfortable with although I can throw nearly as far from a non hop x-step, but I tend to spray more left and right without the hop. I feel the hop helps pivot the body back in the backswing as you move forward, it's more like a dance move and it adds rhythm and consistency on long bombs, and more weight shift which helps direct the energy more forward.
Will's technique seems to be the hardest to replicate, it's actually similar to a backhanded bowling technique. His technique is also quite similar to the Jarvis brothers but his posture is more folded and hence doesn't quite throw as far as them as his rotation or speed is restricted, but this maybe a compensation for accuracy as he is braced to the max like throwing the momentum of a bowling ball against the front leg.
The first frame of your pic, looks like you are hopping too far forward, as your balance is leaning forward. The hop should be a little more vertical so you don't have to lunge your front leg forward so you don't face plant. Going more vertical also helps load your weight more back(down into rear foot as a scale would read higher than your actual weight) into the rear foot/leg/hip as you come down and then stride forward to plant, then brace the lower spine against the front leg so the scale would then read higher than your actual weight but still maintaining dynamic athletic upright stacked posture(skier turning). The front leg has to resist turning to torque/post against it.
In the second frame of your pic, your arm is already hugging. Your elbow never has a chance to get forward so your release is really like a foot or two behind where it should be, see Masterbeto vid where he talks about "going from back here to up here adds anywhere from 60-100' or more". You should either have your shoulders turned back another 45 degrees with the same arm/disc position, so your right shoulder blade is facing the target, or your elbow should be forward of the shoulder with the disc near the right pec at that point. Your posture is not stacked with the shoulders over hips over knees over toes. Rear foot is flat on the heel and TOES OFF THE GROUND! Try throwing a jab with your rear toes in the air and heel on the ground, you can't move your weight forward into the snap of the jab that way.
The third frame is massive hugging and high shoulder and rear side posture/leverage gone trying to push off the rear heel. Your upper arm should be more Barry Shultz/Nate Doss wide, so the shoulder and arm are more connected to whip a heavy momentum(sledgehammer) forward. Your shoulder is too high, far ahead of the arm and open around to the target, so your whip ends up around your body to the right instead of straight through your core/center targetward from a lower shoulder position unless you are content throwing high anhyzers and rollers.
