Good luck with all of this, Richie. I certainly look forward to your final conclusions.

Just one comment for the moment. The fact that a 17thc ballad says 'to the tune of' which is indeed the actual ballad itself. This is quite common and in no way presupposes an earlier ballad of the same name. It could however be referring to an earlier printing of exactly the same ballad. It was just a common quirk of the genre.

The BDBB printing of c1690-96 is indeed the earliest extant printing and I haven't seen it registered in the Stationers Register, but I only have access to Rollins's book. I do believe there is a scarce more comprehensive listing available that might throw something up. Either way it is quite likely that there were earlier printings of the same ballad. Back, Deacon etc did frequently reprint material from earlier copies of the monopolistic printing houses.