#1. Talk to your farrier and see what they think about the frog cracking and dry hoof. Has you farrier said anything about how to help your horse's hoof stop cracking and get healthier? If it has been cracking since summer, and your farrier has not given you any advice on healing your horse's hoof, I would seriously consider switching farriers.
#2. I would go barefoot, there are so many stories about people trying almost everything with horses that have terrible hooves and then going barefoot and the horse being better, not perfect, but much better. No, this will not happen to every single horse but more often than not, it will help the horse. You may think it won't help or will make it worse, but well there is a good chance it will help your horse.
#3. Does your horse have enough nutrition in his/her diet? Often horses with bad hooves are lacking some vital nutrient.
#4. You may want to consider getting your horse on a hoof supplement, something with biotin.
“Good things come to those who wait… greater things come to those who get off their *** and do anything to make it happen.” - Unknown