I’m confident the installer doesn’t touch iptables or firewalld. The plainrouter and router and other stuff in .fogsettings is only for configuring DHCP. I think that DHCP is messed up.
If you modify /opt/fog/.fogsettings and change these fields:
dodhcp='Y' bldhcp='1'To:
dodhcp='N' bldhcp='0'Then the FOG installer will never again touch the DHCP configuration or DHCP service. Then you can configure /etc/dhcp/dhcpd.conf the way it needs to be for your setup. Feel free to post this file to get help with configuring it if you need.