It occurs to me that I have learned more from well-informed people like you on this message board than I ever did from my highly esteemed professors in graduate school.
Anyway, I regret to say that I will only be able to graze the Marmaduke-Shelby business in my Prairie Grove book. I point out the fabrications in Shelby's Cane Hill and Prairie Grove reports and in Marmaduke's Prairie Grove report. I don't go any further, however, because the manuscript already too long and I am in the process of cutting, not adding, material. Sadly, I was born with a near-fatal tendency to become sidetracked by peripheral issues. Last month, for example, I realized I had wasted a week researching and writing four double-spaced pages on the role of Mrs. Harrison (the "lady in black") in the cavalry fight at PG. I came to my senses, such as they are, and reduced the four pages to one paragraph but I could do nothing about the lost time. This, of course, partially explains why the %&*#! project is taking fifteen years to complete.
I certainly hope you find a way to get your work on Marmaduke's raid into print.