You say Elnora was born about 1860 - there is an Elnora Grim listed in the 1880 census, born about 1859.
J. L. GRIM Self M Male W 50 OH Lawyer OH OH Elizabeth GRIM Wife M Female W 48 OH Keep House PA PA Elnora GRIM Dau S Female W 21 IN Teaches Music OH OH Mary GRIM Dau S Female W 13 IN At School OH OH Roanoke, Huntington, Indiana Family History Library Film 1254285 NA Film Number T9-0285 Page Number 544D
I also found this family in the same place in 1860 and 1870 (father's was named Josiah in 1860).
Next, I went through Felker families in Evansville in 1900 and really couldn't find a match for Sarah - I found one family that had a wife named Sarah but her age was off by ten years and none of the children appeared tomatch William. She may have moved in from elsewhere looking for work since she was widowed.
It makes sense that Elnora was Carl's mother.She probably died or divorced John Bunch between Carl's birth and 1900 when the census was taken.You could ask for a lookup by one of the Random Acts of Genealogical Kindness volunteers from Vanderburgh County http://www.raogk.org/indiana2.htmhttp://www.raogk.org/indiana2.htm