Static routes when using iptables killswitch

[Hardrock]

Hi all, hope everyone is doing fine today.

I have a little issue with my iptables which as been setup as a killswitch in the event my VPN fails. The killswitch works absolutely fine on either my Linksys router or Debian build BUT if I try and add a static route 'ip route' to bypass the VPN it simply doesn't work. Would anyone with some knowledge of iptables steer me in the right direction? Ruleset below

#!/bin/sh

iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X

iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT ACCEPT

# Enable routing.
echo 1 > /proc/sys/net/ipv4/ip_forward

# Allow all inputs to firewall from the internal network and local interfaces
iptables -A INPUT -i br0 -s 0/0 -d 0/0 -j ACCEPT
iptables -A INPUT -i lo -s 0/0 -d 0/0 -j ACCEPT


iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT
iptables -A INPUT -m state --state RELATED -j ACCEPT


# Allow postrouting to tun0.
iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE

# Enable forwarding from the LAN to the VPN (and back via related and established connections).

iptables -A FORWARD -i br0 -o tun0 -j ACCEPT
iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT