Hi 1920 census (Heritage Quest images) for Elliot Township lists Emily Watkinson, age 25, as single, living with widowed mother, and teaching in Elliot township.Same census has Harry A Wakefield, age 33, living with brother Walter H, age 32, both single.Ancestry.com (basic sort, no image available to me) 1930 census indicates Emily W and Harry A Wakefield married and in San Joaquin county.As you've probably know, Harry does not show up in CADI.If his death was in-state, this combo of info would indicate to me his death was most likely between 1930 and 1940.An out of state death post 1940 due to WW 2 service doesn't appear likely based on his age at start of war.
You might get a little closer on date using directories at Stockton mainlibrary. I've had pretty good success using this approach on earlier ones where they list all "telephone capable" members of the household.In one case, husband and wife were listed one year, wife only (as widow) next.Might not be a useful for 1930-1940 era as they shifted to telephone numbers, unless there's a change from one listing to the next.
If you're not local so you can try library, it appears Nancy Melton (email@example.com) is offering look-ups for following Directories:
1925 Stockton & San Joaquin County Directory 1935 Stockton City Directory Including San Joaquin County 1940 Stockton City Directory Including Lodi 1942 Stockton, Calaveras, San Joaquin, Stanislaus & Tuolumne Cos. Telephone Directory 1945 Stockton, Calaveras, San Joaquin, Stanislaus & Tuolumne Cos. Telephone Directory