Connect the modem to the test jack at the NID using a short (6ft or less) cord, and check the line stats again. The distance from the CO is your main problem, but you also need to check for any possible issues with your inside wiring.
There is not really anything you can do to improve your connection, other than moving closer to town. If there is a Best Buy within a reasonable distance, you could try a newer modem. They have an Actiontec C1000A in CenturyLink packaging for $99. If it doesn't help the connection, return the modem for a refund.