At 7.2v 6cell charging discharging stops at 4.28v ? for 6 cell 7.2v normal is 5.4v
I don’t know exact solutions.Batteries are discharged with 10-ohm resistor.
You will have to recalculate R1.R13 for different charge currents.If the measure charges current with a multimeter set to ‘A dc’, damaged then it still correct, nothing will be damaged.I found detailed information from here(usawriters.org/).