Regarding evidence that McCarver was not part of Rust's brigade proper, emphasis should be placed on his statement as follows:

http://texashistory.unt.edu/ark:/67531/metapth39854/m1/76/
Stirpes, Volume 37, Number 3, September 1997

McCarver says-"…April when we crossed the Ms River, landing at Memphis- And reporting to Gen Price, whence we were ordered to Fort Pillow. Here the troops under my command, less my own Regiment were turned over to Gen Rust. Soon I was ordered with my own command and the Montgomery fleet of gunboats to drop down to Fort Randolph and take post there."

This clearly indicates that McCarver turned over Turnbull's & Lemoyne’s commands to Rust, while McCarver's own so called regiment remained separate from that command [for the time being].