I've read some of your other genforum queries to familiarize myself with your family.
Have you considered the Emaline Crosslin living in Polk Co, MO in 1870? She's 10 years older than your Enoch Hickam if the census data is correct. However, on George Hickam's WWII draft registration, he said he was born in Polk, MO.
1870 United States Federal Census Name: Emaline Crosslin Age in 1870: 22 Birth Year: abt 1848 Birthplace: Missouri Home in 1870: Jackson, Polk, Missouri Race: White Gender: Female Post Office: Humansville Jessee Potter 64 Nancy Potter 47 Hiram Moore 21 Emaline Crosslin 22
Have you found Enoch and Emaline Hickam on any census? I saw the 1900 Shannon Co, MO census where Mary, George and Eva were living together, but no parents were in the household.