He's a nice looking horse. He has obviously improved and gained weight since being rescued. He still needs to fill out more before heavy work.
I would have a vet give him a thouough exam. The vet can give you a good diet plan and let you know what kind of work schedule to follow. Also, he can let you know what to look for as far as possible health issues as sometimes horses in really bad situations and undernourished need additional care.
Good luck. He's a lucky boy.
Give him a few days to settle in. It is a good time to do a little ground work and spending time getting to know each other.
If you ever find yourself in a fair fight, it's because your tactics suck. ~ Marine 1SGT J. Reifinger