I'm sorry I don't have anything on your Earl or William Playford. Have you checked the census for William Playford, since Earl was born in 1891 by the information of the Org. death index. You may be able to find William in the 1900 census since they give the names of children. You said the service record and grave stone have different dates on them. He could have fudged his age to go into the service. You can also write for a copy of his service records, they may give you some help there. Now there were Playfords in PA. and N.Y. You may want to check there also. It took me sometime to connect my George Playford to his Delaware Co. PA. roots. My George had a son Samuel and a grandson Earl but, they are all buried in Zanesville. There were not many Playfords in Zanesville. Most of them were in PA. and N.Y.
I did find a William G. in KY with a wife Amy who was born in Ind. 1910 Mircode index census. Living with his father and mother who were both in there 50's (father and mother) Good Luck.