Okay, now we're getting somewhere. No hay before he goes on pasture, no haystretcher, less trotter. Maybe look into slowfeeder nets, his evening 2 flakes in that net might last him through breakfast. Then he's got pasture all day, and again, only a handful of the trotter and 2 flakes of hay in the net for the night. The slowfeeder net will make him eat a little per bite, it will last longer, he won't just shove it in, because it doesn't run out so fast. He needs something in the stomach, no more than 3-4 hours without anything or you'll have to deal with ulcers.
As for exercise, trotting. Lots and lots of trotting.
A ration balancer would be ideal, actually, as others have stated. Instead of the trotter. With one lb daily he gets all the nutrients he needs.