If you press your thumbs down on the sole around the frog apex and it gives, you've got thin sole.
Have faith in the boots. They cut transition time in half. The magic is in the padding. Or, you could dump 4'' deep pea gravel where he goes, like gateways, loafing areas, around the water trough. Excellent 4-way developer, support, thrush elimination, toughener. If he lives on the terrain he rides on, he's good to go. I'd use boots when riding for now, but would put him bare on this stuff so he could do his homework on his down time and give him every reason to move around on it. He'll forge/trim his own foot and the wear will promote growth that will get that pathology off faster with thicker soles being promoted as well.
No, two months isn't long in the scheme of things, but if you both do your homework, you'll fly forward. He'll think he has rock crushing feets and out of those boots long before a full wall length has grown down.
It's like a snowball rolling down a hill. The beginning is usually your darkest hour, but then you get rolling faster and faster. Add gravel and you can kick that snowball down the hill and with better results, cause you'll be able to ride those rocks out there with nary a thought and only booting on the longer trails as a caution.
Digital xrays are best, but expensive. The cost for this machine for the vet is downright inhibiting. If your vet has the old machine, they should be cheaper. If you don't think that there are any navicular problems, just the laterals may do.
Are there pics posted somewhere?