IPTables can not easily be turned off via the /proc interface or by removing modules.
But messed up rules can be replaced by the following as long as the modules thmeselves are functioning properly.
echo "Stopping $Firewall"
$IPTABLES -F
$IPTABLES -X
$IPTABLES -P INPUT ACCEPT
$IPTABLES -P OUTPUT ACCEPT
$IPTABLES -P FORWARD ACCEPT