I find it obvious that he bucked and ran, it was hi first time in freedom in over a year. And also fairly normal to want grass when he hasn't seen that in a year.
Why not turn him out before and after working with him so he has some freedom in his life again?
I once saw a 32 year-old mare, a rodeo bronc, buck it's rider off over its head for a solid -0- score at the 1976 Tucson Rodeo, Tucson, Arizona. Even with horses, old is relative. Each animal is different. Likely this horse is as structurally sound as a much younger horse, just out of shape. I liked the day-by-day system outlined by a previous poster.