|My advice would be to spend around $50 (USD) and buy a SOHO Router.|
This would solve all your issues and get rid of that crappy USB network interface.
With your present setup, all you should have to do is enable ICS (internet connection sharing) on the USB NIC with the external connection.
I'd still get a SOHO Router............
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.