I use Pledge, furniture wax on the gunstocks. Wax doesn't stay on in layers, or stay on for very long regardless. you can buy a good paste wax like you might use on a car, but I don't see the point.
Buttplate is an individual preference. A leather piece has been done. Sometimes a true boot is done. If you look at the fancy doubles, they often have a leather pad that is about 1/2 thick, and is fitted over the butt of the stock. I don't know what is in the middle of the pad. Check Brownell's Catalogue for something like that. Or contact Briley's which seems to specialize in making fancy shotguns with expensive leather recoil pads. They do look nice, and they do work. But leather has to be maintained, almost as much as the rubber, and synthetic pads do. Keep them away from heat, and follow instructions on treating the leather regularly with a preservative.
I used a modern recoil pad not because I could not handle the recoil, but because the factory stock is so short, I needed to add length to it to be able to use it. The pad I found just Just long enough to make do. You can look at the TOTW catalogue on line, and they have steel, or brass, or German silver buttplates that might also be considered. Pecatonica is another source, as I suspect other suppliers, like Cains, Dixon's, and even Dixie GWs.
Is that measurement of the bore made at the muzzle, or further down the barrels? If it represents the true bore diameter, its a little on the tight side for a 12 gauge, but that is okay. The 12 gauge wads will all work properly for you. Is there any indication that either barrel is choked at the muzzle? Often markings on the barrels, either top, side, or bottom, near the breech. Or sometimes you can tell putting a good light down the barrel shining back to the muzzles, by the rings of light you see about an inch back of the muzzle.
