Not sure why you are continuing with off bridge setup?
You dont have enough ports ( with 5 on hex ), you need 1 for client on Main WIFI router subnet, 2 for 1790, 3,4 for switches and 5 from wifi router???
In terms of vlans, read this.
http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1