OP
if your method of getting your horse to lower his head and use his back is to pull his nose in and apply spurs I can see why this would evoke a lack of merriment in your horse.
Especially if he has a neck problem.
Just because a trainer has gone up to GP means nothing. There are plenty of riders and trainers who ride front to back. Who use short cuts and are completely oblivious when the horse gives signs of being uncomfortable or in pain.
I understand your reluctance to post videos as some people take it as an opportunity to eviscerate the rider.
In this case, i think it would be helpful but I respect why you wouldnt want to.
I’m not sure what kind of response you are looking for. You’ve had experts ride and watch you ride so what are they missing?
If you keep getting unseated when he spooks and he bolts to the point where he refuses to slow down or stop , then I respectfully suggest that your horse is behind the leg to begin with.
You may want to work on the relaxation and submission process.
This is a suggestion from me because I rode without any kind of connection for years and was completely oblivious to whether my horse was in front of the leg or not.
Sometimes trainers dont talk about this because as you move up the levels they take it for granted that you already know , or because they cant tell themselves.
It is something that you have to learn how to feel and pay attention to what the horse is actually telling you as opposed to what you assume the horse is doing.
One last question for you: Based on info you’ve posted ,
What would have happened to this horse if you hadn’t taken him?