So far I have not been able to find any recorded documentation that would prove beyond a doubt that William Isner was a son of Thomas and Magdalene Miller Isner.However, I have found a great deal of solid circumstantial evidence in the records that indicates that they were William's parents. After 20+ years of research I am 99% sure that William Isner was a son of Thomas and Magdalene Miller Isner.
In regards to your question about Thomas Isner's parents, again I have found nothing in the records that shows Michael Isner even had a middle name. Also, I have found no record that shows who Michael Isner married. The information that you have, and many people are assuming to be correct, appears on the monuments erected just south of Elkins, WV by Mrs. Rannah Isner Britton. She found the marriage of a Michael Wazenor to Ann Maxwell in the Pennsylvania records and assumed that to be the Michael Isner that later settled in Randolph County. I have found no documentation that would prove her assumption to be correct. The records show that the date of Michael Wazenor's marriage to Ann Maxwell was about a year after the birth of Michael Isner's son Thomas. That in itself doesn't rule out the possibility that she is right. There are several other reasons why I do not believe Mrs. Britton's information to be correct.