I've sort of finished but am not sure it was worth it. Not being able to verify the source without first having followed the three kinds of advice meant that a lot of guess-work was required - and with a carte blanche grid, the 12 doctored entries were far more than there should have been, IMO.
Now I have only to add the bars, a chore with the possibility of slip-ups. Why not just allow the solver to appreciate the PDM and leave the grid unchanged? Messy, certainly, but that's not our fault.