Excellant work!
I look forward to your book. Some of what I have been researching in Jefferson County revolves around Walkers Texans from December 1862 to April 1863 when they camped at Camp Mills and then Camp Wright, which is now the University of Arkansas at Pine Bluff.
You are Quite correct that Camp Nelson was where it was to act as a responce force to counter Curtis' advance on Little Rock in 1862. It later acted in conjunction with Camp White Sulphur Spring at Pine Bluff to counter any advance from Helena by way of Clarendon, Ar. The Confederate tactical plan all along was to direct any attack on Little Rock to have to come from Searcy and that is what History shows to have happened.
I call all of this "the War that Arkansas forgot" while everyone knows about the battle of Praire Grove and others in the Northwest, everyone overlooks that there was a tactical battle going on in the Southeast to keep the yankee's from using their navy to come up the Arkansas River. While the Confederates never won any of the battles associated with the area of Operation, such as Arkansas Post, they were successful in directing the Yankee attack on Little Rock to have to come from Helena by way of Searcy and Brownsville without the aid of the Union gunboats.