Sharpe and many others had access to PB's later (BL) manuscript as it was passed around from pillar to post. He was trying to sell it but nobody would buy it. It has lots of material in it but mostly made up of items copied from ABNS, stall copies, local pieces and his own poetry. Just as PB had access to other mss at the time and lots of PB's pieces were entered in Motherwell's Ms.

Jim, if you haven't studied the material I don't know how you can possibly snipe like this.

Richie, some of your puzzles are impossible to answer. Many printed versions did not survive, just as many oral versions did not survive. The best way of reaching any conclusions is to compare as many versions as possible which is what you are doing. I'll have another look at the FMNS version but it is mostly made up of bits from other ballads anyway. As you said yourself it had little if any influence.
It could easily have been put together with bits from more than one version as well.