Nice write up. Thanks for sharing. An easier way to get started with 3G and RPi is using a TP-LINK TL-MR3040. Plug the 3G modem into the TP-Link's USB and the RPi and the TP-Link's with an Ethernet cable and you're good to go.

http://www.tp-link.com/en/products/details/?model=TL-MR3040