Toadfrog,
To attempt an answer to your second question I presume you mean by 'Popular Ballad' a Child Ballad. Only guessing but I doubt if FJC was aware of it. Had he been he might well have included it: Regardless of its possible ancestry it has many of the hallmarks of a popular ballad, and IMHO many of the ballads he did include have very doubtful ancestry as he often commented on himself. Many of the higher numbered ballads can't be traced back any earlier than 1800.