I've gone back & taken a look at the 1865 Sharon Church baptisms and compared the names of the baptized African-American infants - a parent’s name was listed also – with "Dan" & Ellen Walker’s children as listed in the 1870 Charlotte Township census (they were in Charlotte in 1870 & back in Sharon in 1880.

I wonder if your ancestors Daniel and Ellen were, in fact, the Dan and Ellen held by Dr. J. W. Ross prior to their emancipation. I think this because an African-American woman who was a Sharon Church member in 1865 named Ellen was the mother of a baby named James (middle name Columbus) baptized at Sharon in 1865. In 1870, Dan and Ellen Walker had a son named James who was then age 5. Maybe Dan chose the surname Walker because he was born on the Walker plantation?