Excellent effort and write up AH.
Pure conjecture, but looking at the surface related survey, it would seem that the fluctuations in sump 10 could be caused by variations in flow from swallets P1 to P6, (Dr Jacksons, Gautries, etc., P7 has already been traced to the second streamway in P8 I believe), also maybe the legendary swallet in Coalpithole Rake.
From various descriptions, it would suggest that most active development beyond this point is likely to be phreatic with the likelihood of abandoned higher level stuff as evidenced in the western faces of Eldon Quarry.