I like to turn them out in an arena , or other enclosed small areas, and get
Do you have a round pen? Turn him out in there with a ball or something so he can be outside for a little bit without getting worked up.
Try and break up his day and keep his mind occupied! Split his feeds into smaller meals more regularly, stable toys, mirrors, grooming...
Go out to trail and hand walk him there. Treats, cuddles, and kisses are the best thing for a pony that has been in the stall for so long (at least that's what I believe). Try to use this time as a bonding time for you and your horse. Give him a good pamper (ie: grooming, bath him) and use the time to your advantage. You can deep clean all your tack, get to know your horse better, and a lot more!
I wish you the best of luck with your pony and I hope I helped!
Turn him out in the arena or hand walk him on a trail
Borden buster toys, like the ones they have to roll to get the treats or grain, or the hay bagels where they have to pick something up and move it to get to the hay.
Treats, kisses, love, cuddles, hugs, and a good grooming session