Unfortunately there are many different Martin lines and you can see this just from looking at the Martin DNA project at Family tree DNA. Many with the surname Martin are not related.
Your Martin may have gotten the surname from his mother not his father. Women in general loose their surname. Unless you can find a will or estate record that you know is your Tabitha I dont see how you will prove what Martin clan she might have belonged to. Did she have any daughters that you might be able to find a descendant to test her MT-DNA? That might help in understanding who her mother line was. I have many women I cant trace and even men because no estate or will records found.
Just so you know about the Isaac Martin line of Wilkes. They were VERY WELL EDUCATED. Dr's and Lawyers and wealthy. Their Wills go on for generations. Some of this family escorted The Trail of Tears.
Our Martin's of Gunpowder Creek Burke, not one left a will. We only have estate records on a few of them. In general The Very Well Educated usually left wills and they are precise and specific on who inherits what.