All looks quite good.
I’d expect decent performance without the LNA.
Running out of ideas.
Have you looked at the theoretical range? What is the Maximum Range I can Get?
Check for voltage issues maybe:
bash -c "$(wget -nv -O - https://raw.githubusercontent.com/wiedehopf/adsb-scripts/master/throttled.sh)"
Pretty much no matter what the LNA should improve the state without the LNA.
Edit: good catch @Dxista