The numbers are looking better to me. You could even set the gain one or two steps lower ( 38.6 or 40.2)
These numbers still doesn’t match to me.
I doubt the messages of almost 1900 is still to high for 109 aircraft only. But - whatever…
As i don’t know the setting for dump1090-fa on disabling the Mode-A/C somebody else might need to help.
EDIT:
found it. You need to add -no-modeac to the config.
I’ve reported a similar thing last year here:
But different to your setup it only showed the rates on the map, not in graphs. So it could be that your values are correct.
In this thread obj explained where to put the command line switch in the new dump1090 config format.