It’s quite easy actually. To send the data to your local emonCMS, all you need to do is edit this line:
http://emoncms.org/input/post.json?node=1&csv=$GENW,$NETC&apikey=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" > /dev/null
to read
http://your-emonpi-ip-address-goes-here/input/post.json?node=1&csv=$GENW,$NETC&apikey=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" > /dev/null
and you should be good to go.
I don’t use MQTT or Node-RED, so unfortunately, I can’t offer any help with those two.