Your mistakes
1) For wan2 set route metric same with wan1 (100)
4) In "Host monitoring" tab add some servers, ex. Google DNS (8.8.8.8 and 8.8.4.4)
Change wan2's default route to metric 100
Also, i think you need to make processing of external requests thru separated routing tables
1) Routing > Routing tables
Add routing table "alt_wan1" with ordering = only
Add into this table route all-nets wan1 wan1_gw 100
Do the same for wan2 (alt_wan2)
2) Routing > Routing rules
Add rules
wan1/all-nets any/all-nets, forward main, return alt_wan1
wan2/all-nets any/all-nets, forward main, return alt_wan2
still I have no luck with this configuration...
The above configuration I made is also for fail over and load balancing?