I haven't quit yet! Just not finding anything new. One thing you might want to edit in the biography (just to add clarity, I'm not usually a nit picker)
Under your "Notes" regarding his middle name, you say his WWI record says Henry and his FAG says Hoyle..... I think these should be reversed. I have a tendency to give the WWI record more weight, since he actually signed it himself as Emmett Hoyle Jackson.
The only interesting thing I found to look into relates to a Fred Berrie Jackson's WWII first draft record.
"Arkansas First Draft Registration Cards, 1940-1945," database with images, FamilySearch(https://familysearch.org/ark:/61903/1:1:KXWT-1VG : 13 March 2018), Fred Berrie Jackson, 1940-1945; citing De Witt, Arkansas, Arkansas, United States, National Archives and Records Administration, Southwest Region, Fort Worth, Texas; FamilySearch digital folder 005150163.
(not sure this link will work)
His provides his sister's name for a contact person: It's Naoma (Nonie?) Hearn. However, I haven't found any useful leads from this name.
This may be Otis......"United States Census, 1940," database with images, FamilySearch(https://familysearch.org/ark:/61903/1:1:KQJ1-HW7 : accessed 3 July 2018), Otis R Jackson, Prairie Township, Arkansas, Arkansas, United States; citing enumeration district (ED) 1-24, sheet 16B, line 74, family 277, Sixteenth Census of the United States, 1940, NARA digital publication T627. Records of the Bureau of the Census, 1790 - 2007, RG 29. Washington, D.C.: National Archives and Records Administration, 2012, roll 116.
I'll have to sign off for the day.