On that weather underground map... if you click on the blue line of your route, it will give you the current weather conditions at that point. If you click on that blue line in just the right way, you get a white dot...and you can drag that white dot to a different road...let the map recalculate on it's own, and it will give you the time and distance of that new route.
Check the fuel prices in Wisconsin and SD... then compare those prices (use any online fuel site to do that) with IL, Iowa, Nebraska... and see what the fuel savings might be by going through Omaha to Cheyenne and then to Cody WY.
Tolls are going to be an expense too so calculate that, too.