I don’t do that for a living anymore

The answer is an SSH reverse tunnel. Have privoxy running in the rPi listening on localhost. Have it then connect to your home server via SSH with reverse tunnels enabled, tunneling the privoxy port. On your home server you run another instance of Privoxy that’s listening in your home network and proxy forwarding over the tunnel and you’re done.

I used to use this setup for pen testing.

I’m here for Pushing Daisies.