I have a strong suspicion that the Henry Ackerman and Sarah Lemley that you are researching is the same as the pair I am researching.
My Henry Ackerman was married first to a Clarinda Brown.There were several children.His second marriage occurred on September 3, 1854 to Sarah Lemley in Town Scott, Sheboygan County, WI.I have a record that states there was a son James, (which you mention in your posting), plus other children, including my grandmother "Jennie" Ackerman Cole.
My Henry Ackerman was born in Essex County, NY.I know a daughter from his first marriage a Harriet "Hattie" Ackerman Schoolcraft, lived in Fond du Lac, WI at one time.
Please contact me if you think we can be of help to each other.Thank you. Kathryn Cole Baer