overpitched:
1) The lift on the blades is equal. That is why you don't roll upside down.
2) Newton had it right, of course! You can't apply his laws selectively. As you have stated, the first law does nicely. In a downwind turn, there is no disturbing force on the aircraft (other than its tilted lift vector). The "wind" exerts no force on the aircraft, and so the aircraft sees no acceleration in any direction. Draw a free body diagram of the aircraft in flight, see the lift, drag, weight, thrust. Where is the wind??
Aristotle tried to answer this and was quite wrong (in fact, Galileo had to refute Aristotle, and was pounded for trying!).
The downwind does not make you fall, and the boat going upstream needs no more power (someone posted that a while back!!)
This is complex stuff, and can't easily be transmitted in printed word. Needs at least 3 beers and 2 fully articulated wrists to explain most of this. Lets get some, OK?