Normally you can't have multiple route to the same IP that are the same distance out different interfaces. The FortiGate won't let you.
In order to do this you need to enable overlapping subnets.
As long the same IP does not exist behind both interfaces at the same time you won't have a problem. If you do, then your going to have an issue since the MAC address table will show whichever host last sent a packet.
config system setting
set allow-subnet-overap enable
You only need to have a gateway IP in your route if the IP address/range you're trying to connect to is outside the range of the interface itself.
You diagram doesn't include Port IP addresses of the FortiGate, but i would assume that Wan1 has an IP in the 192.168.1.0/24 subnet. Not sure what IP port 2 has right now, but it's not ia 192.168.1 IP obviously.
Once you enable the subnet overlapping you could assign a 192.168.1.0/24 IP to port2 or setup port2 with a secondary ip in the 192.168.1.0/24 range. Once you associate a 192.168.1.0/24 IP to port2 (through either method) you probably won't need to add a route. (not 100% certain about that ... say 80%)
Pretty sure that you can do a secondary IP from the GUI in any firmware version.