This is already a very interesting site, and it's going to be wonderful when you progressed further with it. You've already listed some that I was unaware of.

In answer to: "Does anyone know of other traditional US versions [of Child #2]?", here are two I don't think you have listed yet:

Sarah Ogan Gunning, from Pineville, Ky, rec. 1974
On Meeting's a Pleasure (Musical Traditions)

Sara Cleveland, b Hartford NY 1905, rec. 1968
On Ballads & Songs of the Upper Hudson Valley (Folk Legacy)

Also don't forget the 'Inter Diabolus et Virgo' version of Child #1 from 15th century England, in his second chapter of 'Additions and Corrections" - the version that finally convinced the Prof that here was indeed a Devil ballad.

More from me later.