Okay, the first question I have (purely out of curiousity and not trying to start an argument) if you have cable modem why are you using 4G? If I had any other possible option for internet available I would never submit myself to the pain that is Verizon 4G.
I have kind of the same configuration but I am using PC with wifi usb adapter to be the routers connection to the internet. That is why I am totally annoyed I can't tether as that would be so much more stable...
Because I could! And the upload speed of my 4G kicks Roadrunner's by about 5x. Sometimes I need to do a fairly large upload to my server.