Nighthawk in IP Passthrough mode

We have purchased Netgear MR1100 routers.

We want to operate one in IP Passthrough mode with a public IP address.  We are in the process of getting this service (public IP address) from ATT.  We will not, in this device's configuration, use the WiFi hotspot for connectivity. 

Moving beyond that to run the device in IP Passthrough mode you have to tether the USB port to the PC (in our case running Ubuntu 16.04). In this configuration we will not be connecting to the MR1100 via WiFi (in fact you can't in this mode).

It appears that there is no other way to charge the device except through USB.  We envisioned running this device for extended period of time (days) essentially unattended.  I looked in the Netgear site and there were multiple questions and comments regarding the battery charging/discharging and power management turning off the device.   BTW, I tried to register my devices at Netgear but they said the devices were unavailable.  So I am asking the questions in this site.

A couple of things, first there are no power specs that I can find in the Netgear User Manual.  From some of the posts at that site it appears that the operation of the MR1100 could require much greater than 2 amps.  This was brought up in discussions regarding removing the batteries in order to prevent thermal shutdowns and restarts.   However none of these discussions indicated they were running in other than the "non IP Passthrough" and they were connected via an Ethernet cables.  And as mentioned there was no quantification of the power requirements.

So my questions are:

1. If we run in IP Passthrough mode, what sort of current will the USB port have to provide for the device to remain operational? (the USB cable will be connected to the Lenovo ThinkCentre computer running Ubuntu 16.04

2. Is it possible to power the MR1100 by some external supply while still running in IP Passthrough tethered to the PC via USB? If so how?

3. Is the MR1100 even a candidate for this operational mode as described? It's starting to sound like it is not.

Thanks for reading through this length post but we are looking for answers.

Jim