It shouldn't download anything from the internet if you're just booting up from the Recovery partition. Restart your computer, hold down the Option key when you hear the chime, and choose the Lion Recovery disk when it appears. Choose your language then choose Disk Utility. When the Disk Utility window comes up, select your main HD in the list on the left hand side (the indented name, not the name of the HD brand itself). Then on the right, click on the Erase tab. From the dropdown menu, choose Mac OS Extended (Journaled) and name the partition Macintosh HD.
You don't need an internet connection for any of this.
As for the USB, I've never installed OSX from it before, so maybe someone can help you with that part. But you don't need an internet connection for that either.
First thing's first though. Partition your hard drive first. Again, you don't need internet, you need Disk Utility. Something is definitely wrong if it's taking 72 hours to do anything. I downloaded and installed Lion from the App Store and it took about 4 hours to do it via internet connection.