Very long time & no posts.
So i have done a couple of these setups before to add an internet connection to sites where it is not available.
I usually simply connect the USB modem to the Router, Set the router up to "3G Modem Router" Mode, You get some drop downs for the ISP selection which are:
Location: New Zealand ISP: Telecom Dial Number: *99# APN: Internet
You can put in the user name & password but never have put anything in.
Anyway it won't connect or recognize the device, I have done this twice before with different version routers of the same make & model.