Well, other things to consider...
do you plan to stay in this house for the long-term? If so, maybe replacing the windows with energy efficient ones would be worth it. If not, there are still short-term things you can do that don't cost a lot of money, like weatherstripping doors and windows, using insulated curtains on the windows, taking advantage of any solar warmth you get (opening curtains by day, closing them as sun goes down), getting used to sleeping in sweatpants. An auto thermostat makes it a breeze to set temps to go down when you're at work, and cycle on when you're home. I also have a timer on my electric hot water heater; no use keeping all that water heated all day long for a single person. I have it go one for just 3 hours a day, and never have a problem with no hot water.
If you want to find other ways to save on fuel bills, check out:
http://www.energyguide.com/default.asp
It's a great site that lets you "analyze your use" (2nd tab at the top).
You sound like you have a good head on your shoulders; i'm sure your fiance is lucky to have you.