It really depends on the involvement and the subsequent arthritis - fracturing a coffin bone is not something I normally would say has absolutely no adverse affects - it is something that can be managed, and a portion of horses do go on to their previous level of work, but again, usually with management. It depends on the type of fracture, if there is joint involvement/arthritis, and the quality of layup.
I don’t see “aggressive go-getter” in the video. When I think of a difficult, aggressive jumper ride I think of Rothchild. I hate to harp but I really would consider stepping back and exploring any physical causes.
Horses lift up their heads to keep the jump in their vision - it gets worse if they feel that a rider is holding their face, or fighting them.
It looks like you reconsidered your “shadowroll question” - In my experience, people often use shadow-rolls for horses who tend to try to distract themselves around course and get too looky and ‘up’ - it obscures part of their vision so they tend to “focus” more on what is in front of them, but it does come at the cost of them not being able to see the jump as well, which causes their head to go in your lap - not necessarily the result you want for your situation.