I suspected that the "Colonel" may have been an honorary he received or was given as a "southerner" or a mistake that's been handed down as fact.
When alive, his granddaughter reported that her grandmother (second wife, Lenora Roach Eades), was pregnant when he went off to fight the Yankees. He told his wife that it did not matter if the child was a boy or girl, that when it was born it was to be named "Jefferson Davis Eades." Thus, the daughter was named but went by the nickname of "Jeffie."
Along with Preston Eads, a John Eads is listed is listed, both as Pvts from Cooper County in Civil War Prisoner of War Records, 1861-1865. It states they were captured at Milford (skirmish at Blackwater River Dec 1861). John was discharged but Preston is sent to Vicksburg.
You mentioned the Marshall Family connection in your post. The widow Lenora Roach Eades married secondly in 1865, James Marshall. By the 1870 census she is widowed again and by 1880, she is living with daughter Jeffie and family. I still haven't been able to sort out all the relationships but Lenora and Col. Preston's daughter Laura married William N. Marshall in 1873. They named their first child, a son, South Marshall. Laura died and William N married her younger sister, the baby born during the Civil War, Jefferson Davis Eades. He was 16 years her senior.
William N. Marshall was 16 when the Civil War broke out. Although all census records state he was born in TN, I haven't been able to track his origins. He appears in Santa Clara California records in 1868 as William Norman Marshall, born 1845, TN (He and Jeffie Eades had a son named Norman so I am assuming this may have been him). Thus far, I haven't been able to find him in Missouri until 1869/70. He appears in the Howard County census in 1870 as a boarder with an occupation listed as a machinist.
If the guerrillas were on the property he later owned, it didn't belong to him then during the war because he was too young. There are some interesting connections; the area was certainly a place filled with interesting activity and who knows, he may have had some involvement as a young man with the guerrillas.
Around 1869, he went into business with James Heberling, a doctor who later became renowned for his writing about his mule. "Dr. J. C. Heberling {is listed as a conderferate private from Howard Co} resumed his practice and continued it without interruption until 1862, when he, with six other prominent citizens of the county, was banished to the northeast for suspected sympathy with the seceding states. On his return home after the war, he found that all his live stock had also been "banished" during his absence, and he was therefore without a saddle animal on which to resume the practice of his profession." (History of Howard and Cooper Counties, St. Louis: National Historical Company, 1883). Marshall also has connections and associations with other Confederates and I have suspected a connection in Saline County.
William Marshall was known as a "sea-faring" man, so perhaps that's why he was in California near San Francisco after the war.
Coordinates of Boone's salt lick owned by William and Jefferson Eades Marshall are N 39° 04.919 W 092° 52.754 It is now a state park. If you enter the coordinates into Google maps, you can see that Arrow Rock (Saline County) is just across the river. There is an 1880's Howard County Atlas online that shows his extensive land holdings all along the Missouri River.