Great job in researching your gggrandfather, and thanks for sharing.
You bring up an interesting observation:
According to my understanding, the Legion was on the way to Arkansas when they were ordered to go to Vicksburg. Waul's Texas Legion was sent to the north of Vicksburg...
I have seen mention of Waul's Legion near Tyler, Tex., which became the gathering point for Texas regiments en route for Arkansas.
I would be interested in what led you to this understanding.