Hi Brian,
It's very common in oral tradition especially with such older pieces for details to be removed from one part of a ballad to another or from one character to another, as forgetting and recreating take their toll.

In this case although there are likely many interim versions that haven't survived it should be possible to postulate some sort of evolutionary lines, and Richie is the best man for the job.

I don't think there has been an in-depth study of this one using all of the extant versions.
It is beginning to look like the ballad originated in London (like many early ballads) but received most of its more drastic evolution in Scotland before being returned to England in a reduced form, where the 'Acre of Land' versions evolved, probably during the 19thc.