Re: dropping internet and sat tv.

http://www.google.com/intl/en/chrome/devices/chromecast/learn.html

I have streaming devices, including the Chromecast. In order to connect your phone to Chromcast they must both connect to the same wifi service. (See link above). I don't believe the set up you are proposing will work.
I suppose you can test it by turning off your current modem and router and see if it works.