The quick fix would be to get a smaller chain ring and remove some links from your chain. Of course if you are not very savvy this might not be as quick as fix especially if you have a chain guard. You haven't mentioned whether or not you have a rack/basket, but riding with a backpack will definitely make you sweaty (if you do ride with one). I think you're better off getting a bike with a wider range of gears; a lighter bike won't necessarily fix your problems if the gearing prevents you from spinning up a steep gradient. I'd recommend getting my current commuter off BD (for only $300!) and it has a triple crankset as well as fender and rack mounts. It's a rather heavy bike but the granny gear gives it good climbing capabilities.