Feed very simple. Restricted grass and plenty/adlib meadow hay.
Agrob or thunderbrooks feed with copra or whole soaked oats if needs more calories.
I use agrob ulcer mash plus copra and
Forage plus mineral vits.
I know a few horses benefit from speedi beet too.
Restricting grass and finding...
Get it sorted. Yes anyone can remove shoes. But letting the fall off is pretty dangerous. If you can't be there for farrier pay a groom. And rethink if you are in a position to own as it appears the work schedule you have is compromising horse care...
Check teeth. Worm. If all ok get vet to check him.
Feed wise I use grass nuts (meadow magic), linseed meal and copra. All safe for metabolic horses, which older horses at risk of....
Hacking out. Bit of schooling while hacking. Few trips out to hack at different places per month. Will start schooling in arena 1-2 x week soon and fee lessons/clinics and comps