@sathyashankar 

Loadbalancing, your weights should be 100,30,9 across WAN1,2,3.

It is not clear if you are running any of the ISP devices in bridge mode, or if they are in routed mode.  Where possible I recommend bridge mode, because that means that the ISP assigned IP gets assigned to the respective WAN port on the TPlink device.  If that's not possible, then I would statically assign an IP from the router's subnet (ie 192.168.X.1/24, so assigned WAN IP as 192.168.X.2) and then make this .2 address the DMZ for that router (port forwards all ports).

If you have a public static IP on your 1G connection, and you want those ports to be accessible to the internet, then those connections always have to go through WAN1..which means you need to return those connections to WAN1 and not via the load balancer.  So set a Policy Route for any server/service you have exposed on WAN and force, based on source IP and/or port to go back through only WAN1.  

User traffic will still have the ability to round robin, based on weighting, across all 3 connections, but any service depending on the IP and/or DNS resolution of WAN1 will stop working if WAN1 goes down.