No matter what, keep going. You have started a really good discussion.
Multi-function control surfaces take a little more thinking. Your example had a slight error in it, but here is how a climbing right turn could work. YAW - as you stated and if you have no vertical surfaces, you must open the right wing drag device (you said this well by splitting the right wing control surface). PITCH - Both surfaces have to go UP a little. ROLL - the right surface must go up a little (to lower that wing) and the left one must go down a bit (to raise that wing). Remember that control surface movement in flight (unless you're at extremely low speeds) are very small.
So let's use some numbers. YAW - We split the right control a little, say +/- 5 degrees (probably way too much). ROLL - The right control goes up 5 degrees, and the left one goes down 3 degrees. PITCH - Both go up 3 degrees. Sum the numbers to come up with the right control is UP 8 degrees (5+3) and split, and the left control is neutral (3-3). This will roll, yaw and pitch the airplane the way you want. Also remember control input is only used when the airplane is being maneuvered. (Dang, this is further than I wanted to go). In other words, when you roll an airplane into a turn, you don't continue to hold the ailerons in throughout the turn (or the airplane would continue to roll around). Note: you will need a small amount of aileron, though, to offset (fight) the natural stability of the airplane to want to fly straight and level).
As for control surfaces on the leading edge of a wing ... they are unstable (in this case a very bad thing). As a passenger in a car, hold a small piece of cardboard (like a large McDonalds drink cup) out the window (a cool, cheap wind tunnel). While holding the front of the cup (on the upwind side), you should be able to hold it and rotate it around a little. Now, hold it by the back side (down wind), and try to do the same thing. It is either much harder, or it was ripped out of your hands. Go back and pick it up ;ob........
Thanks for listening, Ron