Loving someone does not depend on looks, this statement "Lastly, and I know this is shallow, but I can't stomach the idea of only being intimate with one girl for the rest of my life, especially WHEN she gets old, wrinkly, and likely puts on a good bit of weight." shows you have a LOT of maturing to do. It may be best you wait for actual love, not the kind you say because its the "right" thing to say. If the hint of leaving someone just because they don't fit into your approved set of looks you do not love them. By the sounds of things you posted, having love and kids needs to wait until you mature enough.
Maturity is not an age.