I think you should stay on the plumb in mod for 3-5 days to test a few shots see if the lower flow/linear fill without the pump breaks gives you better tasting shots.
I understand your concerns about floods/ and the not dead silent mod, but just test if the taste is better. Stay at 1.5-2 bar pi for line pressure, dont go to 4-6 bar as those shots are harsh with 10 bar extraction pi.
Forgot: you can test the flow by flushing in a bowl on a scale for 10 sec. do it 3 times then average the flow per sec.
Do the same or someone else can do it while on pump (I think I did it while on pump and I had 25g/s. Your flow looks like 10-15g/s max.
You can install a kill off valve/switch off valve and turn the water line to the machine off while you are no there for a few days while you do the testings.
PS: another thing to consider now is that if the flow that enters the boiler is less the temperature of the water injected will be higher, it’s not exactly like in a HX system but it’s similar, you might need to bump the temp 1-2C lower while on the water line. 12-15g/s flow entering the boiler gives more time for the heater to heat the boiler instead of 25g/s while on pump.