What recommendations would you have on confirming or denying the following situation?
My ancestor Nancy Jane Culp is the mother of Alonzo Culp (my great grandfather).
Through good genealogy, we know his father is unknown, and he takes the surname of his mother. My Aunt (not a genealogist but intelligent) did a family tree of sorts many years ago but did not source her information, she has since passed. In her tree she has the father's surname listed as Watt?. Questionmark included. I found another Culp researcher who has his father as a James Watt but she does not remember where she found this information and also has no source info.
I found a couple of James Watt's living in Jefferson County, Ohio who are of the right age, one appears to actually be living in Knox, Jefferson, Ohio in 1850, married and a first child, born in 1849, the same year as my Alonzo. So circumstances suggest he is a likely candidate if you accept a dalliance with Nancy Jane at the same time he marries another woman an fathers a child with her.
I recently did a Ancestry.com Autosomal DNA test on my mom and found a DNA match with another woman who has this James Watt in her tree. His father is a Charles Watt and would be the likely common ancestor. Charles is from Ireland.
So I have a coincidence of finding a James Watt in the right place of the right age matching the speculation of two unsourced researchers and a DNA match with someone who has this James in their tree and no other apparent common ancestors. My mom's DNA suggests she is 17% Irish and I have only one other line that is suggestive of being Irish (Nelson). Of course there are other lines that dead end in the USA so there could well be other Irish lines.
So what should I do from here? How do I go about using DNA to help untangle this knot?
Thanks for any help and advice you care to share.