> In the case of the popular "Lord Thomas" broadside there was one stanza not found in tradition, otherwise most were the same ballad versions. Clearly the broadside was based on the traditional ballad and a stanza was added.

I'm not sure what you're saying here. That there are collected versions very similar to a broadside except that the broadside has one more verse? While it is of course possible that a printer picked up an existing ballad and added a verse, personally I find it much more plausible that a printed version passed into tradition and one verse was either forgotten or left out deliberately.

> Since Stockton's kin were in Virginia before the broadside was published it seems that his ancestors learned the ballad in England but not from the broadside.

While that is possible, again I find it more plausible that the ballad crossed the sea later. There was plenty of time for it to do so between the broadside being printed in the 1700s and Sharp collecting from Stockton in the early 1900s.