Improving overall performance

I have a couple of those 3 pole filters. I also special ordered some single pole 978Mhz UAT cavity filters.
They are great for a noisy location like NYC. I have 4 or 5 Mobile cells within a block or two.

Your stats look great. You will have the most A/C within a week.
This guy gets more position reports but could be in a better location
http://flightaware.com/adsb/stats/user/kq5m#stats-38787
You get 10 times as many reports at >200nm so I think you are doing pretty well.
Dave seems to get better reception to the East. Do you have something blocking that direction?

My suggestions, if any, would be

  1. optimise your gain settings
    Tweaks
  2. consider RF chokes on the USB pigtail(for the Prostickplus) if you use one and USB Power cable.
  3. put the RPI in a metal case to reduce noise getting into the dongle
  4. put the dongle in a metal case. I got some form https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ however, they no longer sell them.

I think your setup is pretty much the best value for money. My radarcape only gets about 2-5% more planes than the Fa Prositckplus.