I am going to "sound like a broken record" (no one under 45 knows what means) BUT:
Diet WILL help toughen his hooves up. He may never be able to be ridden without shoes but diet helps.
My 25 yo TWH has always been flat-footed and very tender; he always wore shoes.
He was diagnosed Equine Metabolic Syndrome in 2007 and his diet under went a major major change.
About a year after the change to a very low starch diet, I noticed he went gaiting across the gravel drive without missing a lick.
I decided to bridle him and go down the road to see what he'd do barefoot on the road. To my surprise he went down the road at a pretty good lick and stayed in stones in the center of the road.
I would still shoe him if we were hard trail riding but changing his diet to as low starch as I can get it, has surprisingly strengthend his soles to allow me to ride him barefoot for all the more I do around here.
Both the vet and the Trimmers told me that, while all my horses have great hooves, the best hooves in the barn belong to the two with metabolic issues
Hopefully you find a farrier you can trust
An no, we are not anti-shoes. All my horses are barefoot because (A) I can't ride anymore (B) two of them never did need shoes to go "4-wheelin'.
If I were still riding like I used to, the other two horses would take turns having a set of shoes put on. I would rotate them to force me to ride them both
Anyway, along with hoping you find a trustworthy and knowledgeable farrier, at least give some thought to a change in diet