You most likely didn’t actually change the gain.
A gain of 0 is 55 less than -10 approximately.
Running a gain of 0 with your setup would give you 0% >-3dB, i would pretty much bet on it.
According to your stats page you are using the installed version, not the piaware sd-card version.
That means you need to set the gain in /etc/default/dump1090-fa, not with piaware-config.
See case 2 of this post to see how to do it:
For Beginners - How to Set / Change Gain
-10 is equal to around 55 in most cases.
Next lower gain value is 49.6
You could try a gain of 40 and then 35 probably.
The LNA is very nice but you should try and put it before the 50 m of coax.
You sure you don’t mean 50 ft?
Anyway putting the LNA in front of the coax run or wherever the cable comes into the house is probably connected to getting new cables, so at the end of the run will have to do for now.
Have you ordered a bias-t for the LNA already to supply it with power?
Something like this: Bias Tee Wideband 1mhz-3ghz for Ham Radio RTL SDR LNA Low Noise Amplifier 50vdc for sale online | eBay
Without power the LNA doesn’t work and will just block all signals.