Did another two rounds of measuring the H offsets and found some different values. Probably needed some experience in paper gripping to get the right feel to do it consistently for every point.
first new round:
-0.14
-0.13
0.09
0.16
-0.1
-0.2
0.01
0.09
0.07
second new round:
-0.18
-0.16
0.08
0.17
-0.08
-0.18
0.02
0.09
0.1
New H offset values in the bed.g file:
; Probe the bed and do 6- or 7-factor auto calibration
G30 P0 X-73.6 Y-42.5 Z-99999 H-0.16 ; X tower
G30 P1 X0 Y-85 Z-99999 H-0.14 ; between X and Y towers
G30 P2 X73.6 Y-42.5 Z-99999 H0.08 ; Y tower
G30 P3 X73.6 Y20 Z-99999 H0.17 ; between Y and Z towers
G30 P4 X0 Y67 Z-99999 H-0.09 ; Z tower
G30 P5 X-73.6 Y20 Z-99999 H-0.19 ; between Z and X towers
G30 P6 X-36.8 Y-21.25 Z-99999 H0.01 ; half way to X tower
G30 P7 X36.8 Y-21.25 Z-99999 H0.09 ; half way to Y tower
G30 P8 X0 Y42.5 Z-99999 H0.08 ; half way to Z tower
G30 P9 X0 Y0 Z-99999 S6 ; centre, and auto-calibrate 6 factors
Finally managed to get good leveling now.
Thanks for all the help everybody!!