Having both router and modem with the same IP is asking for trouble. Best practice is to unplug one device, configure its IP to something else and then reconnect.
If you're WAP has an AP mode, AP mode is the way to go. There really is no need to do double NAT. Many businesses mistake the need for a wireless ROUTER when its a wireless ACCESS POINT they really need. For Flow connections a router was necessary because theyd distribute public addresses whereas TSTT modems distribute private.