OK so now I understand. Disregard my post above (what a mess). I was confused about how to set the internet gateway and was thinking I had to do this manually (trying all sorts of crazy things) but then realized that NetBalancer does this by applying individual rules. I was way off!
From what I now understand about Linux IPtables or netfilter is that by creating individual rules in NetBalancer it must be creating PREROUTING and POSTROUTING rules in the NAT table forcing all traffic from one interface (LAN NIC) down another (VPN interface).
Correct me if I’m wrong here…..