A couple of relevant points..... Can't tell from the pictures but the buttstock should only be about 1 1/4" to 1 3/8" or so. Also, the curve on the back of the butt looks like it is a little low, I'd try to adjust to the center or a bit higher. They were typically not much more than 4 1/2" tall too. Which gun is your inspiration?
As you well know from the book you refer to, really curly wood was often seen on mountain guns with out buttplates. WAlnut was probably more common but curly maple is a good historical choice as well.
I have a original NC gun with out a buttplate, it's no worse for the were because of it's lack of buttplate. Also, as you can observe in the book none of the buttplateless guns have much if any wear or damage due to the lack of the buttplate.
Also, looks like you might have some overall "skinnying up" to do. Always hard to tell just from pics.
Looks like your cheek piece may be too far back...of course the original you're copying could be the same.
That gun may look great with a scraper finish.