For the cracks, adding more moisture may not do a darn thing for you. I would roll the toe a tad more with the rasp and wait and see.
Also, if your horse is used to shoes, but wasn't really sore until a few days later, you may be looking and soreness in the leg due to the different way of going. Allow some time to adjust. If you wear different boots, your muscles and tendons can get fatigued. This is why most of the time you should wait to pull shoes after the riding season, when he's least active. Also, the sole may have been thick enough initially to protect the sole, but was soft, and now that it's in more contact with the ground, the solf flakey stuff could have worn out and now it's more tender. Or he could have simply brusied it.
Also, when coming out of shoes, some horses start healing from the inside out and may start abscessing for a period. (seems like horses that had corrective shoes do this the most and more severly than healthier hooves). The increase circulation, is the cause for this, and nothing short of "weathering the storm" will fix it. Abscesses can be the source of mild to severe, constant or intermittent lameness until they blow. The bad news...it's hard to watch and deal with while it's going on, The good news? The horse will have better feet after the abscessing is over ,but you have to stick with it. Shoes can mask the problem, but stop from ever really healing or really slow down the process. The other good news? In more time, new hoof wall will grow down and the cracks should go away.
The hinds could use a tad more height at the heel, but you can see the bevel (mustang roll) which is good.