Well with the signal smashed against -1.5 dB it’s really hard to judge dynamic range.
(The digital signal can to an extent be decoded while the high bits are overloaded as they stay 1, full scale)
Thoughts on optimizing gain
Maybe this thread offers you some hints?
A significant part i could say about that graphs would require more info:
Your gain setting / SDR used / coax / antenna used and its location … indoors / outdoors … possible obstructions.
Then it’s good to see the number of aircraft and message rates from the first 3 graphs or so.