Mike got it right. To answer your "lift in one direction" question, here's my best shot - bear in mind I'm not a physics (or any kind of science) major although I am a pilot:
The typical explanation of lift hinges on Bernoulli and the "sky sucks theory," but that's an overly simplified way of looking at it. If that were the only thing going on, this aerobatic airplane wouldn't be able to fly with a symmetrical airfoil:
A better way to think about it is that the wing needs to push down more air than the plane weighs. If you only want lift in one direction (i.e. you don't plan to fly upside down too often) an asymmetric airfoil helps this by curving the airflow over it so that it exits the wing on a downward trajectory, but if the plane flies at enough of an angle of attack it can accomplish the same thing (essentially, it's presenting a downward-angled ramp to the air). The aerobatic airplane can fly just about as well upside-down as rightside-up.
Since we only have one keel and it needs to generate lift on either tack, it needs to be symmetrical.* When you load up the boat going upwind, you're actually propelling the boat sideways against the water and inducing that same angle of attack that you would have on an airplane wing. The resulting lift vector gives you (mostly) forward motion upwind. You can also stall the keel, just like an airplane wing. If you just point the boat upwind from a standstill without sufficient forward motion, you'll just go sideways as if you don't even have the keel down. That's why you usually have to gather speed on a reach before hardening up to closehauled.
So, if you want to reduce leeway and increase lift, you can sculpt your flat keel into more of a foil (teardrop) shape like the "bulb" at the bottom already has. This is what I did and it seems to be working. I essentially added chord to the shape. There's no free lunch in physics so the penalty is a bit more drag, particularly downwind, but our upwind performance is much better this season to my estimation.
*Some high performance boats actually do have asymmetrical keels - they either use a moveable trim tab on the back of the keel or they use twin daggerboards that they switch on each tack. If you want to see something really nuts look up the "tandem keel" that New Zealand used in the 1992 America's Cup.