I can't answer for who the Levin Willoughby is. What I can tell you is that your Levin Willoughby (1774-1861), married my 2nd great grand aunt, Elizabeth Leby or Liebe (1792-1868). Elizabeth was the daughter of Christian & Anna Musselman Leby of Ross County, Ohio. Christian was a revolutionary soldier from Pennsylvania. I know that there is a misspelling of Elizabeth's last name on the marriage certificate. It is a common thing for Liebe/Leby to be misspelled or have variations. If you have any questions, just ask.
Sharon