If he's like that with shoes, you need pads.
My mare has thin soles, and they're soft too. In the spring she can't walk on hard ground, like cement. No gravel, and she goes dead lame if she steps on even one rock.
Recently she's finally able to walk where she wants.
First off: turnout in the least rocky, and softest turnout area possible. Our outdoor arena is sand/rubber, but has a lot of gravel in it. The pastures are a tad rocky, but with the grass and ground, she's fine in it. The paddocks seem to be clay, and also have gravel in them from the walkway. So, she goes in the roundpen, which is sand and has very few rocks.
Second: 20mg or better hoof supplement. It will grow better hooves, and faster. It will take 6 months to a year to completely grow out, but it will help in the long run.
Third: (Make sure the abscesses are gone or just make sure to avoid those open areas) Find some iodine (I use the iodine wound stuff). Clean and brush the hooves thoroughly before and after you take him out. Then spray his hooves (just the sole, not the frog or heels) with the iodine after you do his hooves before you leave. I do it in the aisle so the bedding doesn't absorb it right away.
Do this once everyday.
Fourth: Venice Turpintine (Turpentine? I just refill my bottle with regular turpentine from the hardware store so it lasts longer). MY mare can only tolerate it every few days or it dries out her hooves. Brush a good amount on the sole and heels the day he's shod (after, of course), and about once every 3 days. If you need to, do it every 2 days. Work up to once a week. Right now, my mare only needs it every couple of weeks.
This needs to be done in the aisle, because the turp. is sticky. After a few minutes he can go in his stall. (MAke sure to close the cap tightly or else it dries out and you need to add more turp. to thin it).
The turp. will toughen his hooves. I see results the next day.
Fifth: Also, once a mouth I put thin hoof conditioner on the sole and frog, hoof oli/conditioner on the outside walls, and thick conditioner on the coronet band.