As per our pm discussion I added the ports 80 and 443 to the hotspot as accepted connections. First time in my test setup at home it worked and I was even successful in changing the WiFi to e different SSID using the iPAD.
Next I changed location, unplugging the router and setting it up at my parents house. This took some trail and error after which I finally got it to work, by disconnecting the power source and restarting the modem. Connection to the Routers network was establsihed, login screen appeared after which I could access the WEB UI again and change to the new locations SSID as WAN bridge.
Back at home I am now unable to conect. After selection of the routers network SSID the login screen does not appear anymore... The WIFi does indicate it is connected to the network. But I can not reach any page via the WAN, nore can I reach the routers web UI. When connecting to the Routers network there is no login screen anymore. So far I've tried several reboots, did the latest firmware upgrade over LAN connection.
Edit / update: I do get this WAN status information.