1. Your TAS quantify the relative speed between the aircraft and the surrounding air mass. So when flying with a tailwind, the plane is moving, but the air is also moving in the same direction...so the relative speed decreases as well as TAS and Lift.
2. It decreases with tailwind and increases with an headwind. See above.
3. It is true for every airspeed but the GS. You can assume he's talking about TAS or IAS if you prefer.
Edit: Of course you increase your pitch to increase alpha (->Cl) to compensate for the loss of TAS. This is true until the stall point, where an increase of the alpha angle produces a decreased Cl value.