There will be probably a bandwidth necessary of around 15kB/s per receiver you connect. Could also be 30 kB/s for a very busy receiver.
Apart from the bandwidth there should be nothing from stopping you connecting as many IP-addresses as you want.
As i said if you feed the combined data, you lose MLAT (https://flightaware.com/adsb/mlat/).
I would therefore recommend install piaware and claiming each receiver separately.
But you can also disable MLAT on the FA stats page and feed the combined data.
Note: won’t work on a piaware sd-card image
For that you need to enable the beast out port on combine1090:
In /etc/default/combine1090 change --net-bo-port 0 to let’s say 29005 like this:
NET_OPTIONS="--net --net-heartbeat 60 --net-ro-size 1000 --net-ro-interval 0.2 --net-ri-port 29001 --net-ro-port 0 --net-sbs-port 0 --net-bi-port 29004 --net-bo-port 29005"
Then with piaware-config you set the following config options:
But again i would recommend using piaware on each receiver, that way you also get the MLAT data for your local map.
(Right now you only have piaware on one receiver as your stats page shows only one)