IP based routing on Openvpn on Openwrt

I am using latest openwrt software on Dlink DIR2660 A1
I was able to activate expressvpn by openvpn settings. but need few help:

  1. Right now configuration has been done that vpn is strictly enforced. when i stop vpn service then the internet gets disconnected. this i want to remove.
  2. on my wan6 i need IP based VPN routing so that when devices connected to the wan6 only the devices mentioned will get VPN tunneling and others should be on normal.

Thank you.

Is IPv6 fully functional with OpenVPN e.g. if you browse to 'ipleak.net' from a client you get both ipv4 and ipv6 showing your remote location?

If so you can look into using pbr: