Thank you for the time you have taken to search out this information. The tree you have mentioned belongs to my cousin, However Wiliam states in his military records that his father is dead by 1919 and Charles P (married to Katherine L)is very much alive. William also says his father was born in Missouri and Charles P was born in Indiana As you say Charles E (William C's son)says that William's father was John not Charles So we feel this is not the right family. Charles E could have got mixed up with his grandfathers as his other grandfather father of Myrtle was called John.
When Kathrine writes to the military asking about her son she does not write Mr & Mrs implying that she is indeed on her own and may be a widow.
We have the information you have found however we do not have an obituary as we have presumed that William would have not had one. William C's father remains elusive and with out this we can not get any further back.