Most welcome, Shadow : ) From what you write, it DOES sound inspired moreso than behavioural. SOUNDS. A horse that shows pain also displays his vulnerability and many horses are unwilling by instinct and laws of survival to be seen as vulnerable in any way. By the time we humans get a bead on “something’s not right”, the issue can be fairly pronounced within the horse. I really do hope you are able to solve this issue without too much trial and errour and continue on with a good rehab plan and a full future with your boy : ) Injuries and health issues are a PIA for all involved. Good on YOU for looking at it from all angles!
Sure there's right and wrong but mostly there's just a whole lotta different.