I have played other games that require a static connection to enjoy while using a smartphone as a data connection. A well known Action RPG series’ third installment in particular. Bout Heaven and Hell and stuff…You get the picture.
Anyways.
You can find Apps that will allow you to use your phone’s data connection as a hotspot. Alternatively, most providers allow you to pay extra to allow the device to do this. I like the free way of doing it, but hey, thats just me.
Depending on the quality of signal you are recieving, you should be able to do this. You will still have some lag spikes occasionally, usually when your device is doing routine check-ins with the network. Any area that you have 3G service should be adequate enough to play with for multiplayer purposes. 4G has a much higher data rate in general, but it sounds like you are rural, so no dice there.
Reasons Im thinking that its ignoring the Upnp and not letting you play:
Whatever method you are using to use phone data for connection is being throttled from streaming data in the method needed to play. This is a network side thing, where your provider puts something into its hotspot service to prevent you from abusing the feature.
Your computer is not treating your device as Upnp.
1 can be solved by using an app, as mentioned before. 2 should be a google-able thing to solve. Im not sure about it myself.
Another Idea I have is to use a proxy to put a layer between your computer and the device. Might trick it into working.
Hope this helps, PM me if you have a question further. Im not even sure what I wrote makes sense.