Go back to flat work only, lots of rapid transitions, walk to trot to walk to canter to walk to trot, etc. When quiet and agreeable, incorporate ground rails and work over them until he trots thru ON THE BUCKLE. Once again, when quiet and agreeable, up the ground rails to cavaletti, same approach with same goals, then up to a full grid or as desired with same approach and goals. Reteach the jumping process. Expect the horse to not take you seriously at first, too, as this is not your usual ride method. Be relentlessly patient as well as consistent : )
I MIGHT consider a minour bit change for reconnecting on the flat (not usually my first choice of corrections and I would definitely stay within the snaffle family) but where the horse is a lease, you would have to pose that to his owner/agent and they might not agree.
Sure there's right and wrong but mostly there's just a whole lotta different.