Hi have you looked into Pete Ramey - he has saved many horses in similar situations.
I do not understand much of the physiology but we did follow the instructions in his book - we had to do it ourselves as we did not have a regular farrier in the area - my horse had special shoeing for years and was always lame with one bad foot; it took us longer than if we had an experienced farrier but his feet all ended up looking like wild mustangs.
From one of his articles:
In thousands of dead horses he examined, Dr. Rooney found that the fibrocartilages surrounding the flexor tendon and the navicular bone were ALWAYS damaged if bone remodeling was present. He found not one single case in which the damage to the bone was beginning, and the cartilages at the interface between the navicular bone and the deep flexor tendon were not yet damaged. Not one case in thousands. Read this again if your eyebrows didn’t go up.
Specifically, the order in which damage occurs is; first the fibrocartilage surrounding the navicular bone (as will any arthrosis begin on the more convex surface), second the fibrocartilages surrounding the deep flexor tendon, then the deep flexor itself, and finally the navicular bone is damaged by the rough surface of the damaged deep flexor tendon. How? Why? Dr. Rooney wondered too. Simulating a toe first landing in test machines with dead horse legs, he was able to simulate this exact process that is the beginning of navicular bone remodeling.
His site :DIGGING FOR THE TRUTH ABOUT NAVI
I truly hope this will help. I do not think it could hurt.