The turnout alone should help. That was pretty limited where he was before right? When things slow down up here, I'll see what we can do about getting extra horses and riders down there ;) How far of a drive is brown county from your new barn?
In the meantime, I'd just change it up working in the outdoor. Doesn't have to necessarily be switching disciplines but change up what you are working on frequently so he has to stay on his toes waiting for your direction and isn't anticipating what you are going to do. Avoid riding tons of circles. Maybe you could set up a trail course in the arena?
Or you could always send him up here to me, I'll take his cute butt riding in the woods behind my barn