Many of us are using a different version of dump1090 called DUMP1090-mutability. This has been extensively changed from the version im the image.
see ads-b-flight-tracking-f21/raspbian-ubuntu-packages-for-dump1090-mutability-available-t19619.html
The wonderful thing about doing stuff on the Pi is you can take out your working SD card and experiment on a new card, then later revert by just switching back to the one that works if it all goes wrong.
You have excellent range now - it may be difficult to get more with the R820T dongle.