I think your cclock is too low, it is capping your hash power.
mine is at 1055mhz cclock and 1240mhz mclock (although I'm locking the core clock which should be better in term of efficiency and temp)
you can try to add more cclock first and see, then if you want, instead of cclock & pl, I suggest you to use lock-cclock command (in miner, or in windows cmd with nvidia smi, or with msi after burner).
with my 3080 gigabyte vision I get consistent 73.5mh/s with this:
1240mhz mclock
1055mhz lock clock
no PL nor cclock setup because when you use lock clock it manages the power itself.
power draw is 220w (but with last nbminer light variation between 208w to 220w but it's ok for me), temp 40gpu/72vram
lhr tune cmd is at 75
nbminer does not manage lock cclock so I use nvidia smi:
smi nvidia: open cmd window in windows then:
#first list your gpus:
nvidia-smi -L
#note the number/index of your gpu. for instance gpu number 1 and cclock locked at 1055mhz:
nvidia-smi -i 1 -lgc 1055
#if you want to reset to default values:
nvidia-smi -i 1 -rgc
and for mclock and fan rpm I use msi afterburner
Didn't work unfortunately. And I did it correctly :/
-500 or +150 on gpu does not matter either.