You could try a bentonite soak to draw the abcess out, if you have access to bentonite.

Another super product to toughen feet is Jimmy Rickens. You just paint it on. Would help with the tenderness, but wouldn't do much if an abcess has started.

Did your vet take a digital pulse? That will tell if an abcess is starting. Did you go to a horse vet or to a cow vet? There is a difference.

We had a horse at one time who had a crack in his foot. It cracked clear up through the coronary band. He was shod at the time, but his foot would move in two parts, like a cows foot. We took him to a vet and he prescribed a wide-web shoe to steady his hoof wall. Anyway, he also said his foot was just about to abcess and didn't want us to haul him home, as the movement of the trailer could cause the abcess. So we left him with a friend who lived near the vet. We avoided the abcess and we were able to bring him home in a few days. He eventually was just fine. That's all we had to do was shoe him with the wide-web shoe.