Question 1: a lift-to-drag ratio of 40 is currently not possible (although a higher value is possible but for a wing alone) due to the significant tether drag during crosswind operation. A value of 12 (with tether drag) is more reasonable concerning rigid wings such like Makani’s wings.
Question 2 : indeed Makani provides a value of 9 m/s for the full rated power wind speed on the Response to the Federal Aviation Authority. Generally the nominal wind speed is 10 m/s or 11 m/s. As an assumption Makani M600 can also be limited by a too high tip speed of the secondary rotors.
Question 3: yes, a lift coefficient of 2, even more, is possible. Planes use flaps to increase lift coefficient. The advantages of using high lift coefficient overcomes the disadvantage of the increase of drag as shown on https://www.researchgate.net/publication/320742362_Drag_power_kite_with_very_high_lift_coefficient.
See also the discussion on FlygenKite.
Note that all my calculations are only assumptions. And also we have not curves based on the real. A comparison of AWE vs wind turbines is not still relevant as AWE has not yet reach maturity. There are numerous factors such like maintenance, reliability, real efficiency, and so on.