As the dark energy passes around the edge of the disc, it begins to move (radiate?) at an angle, as it must eventually close up on itself in order to keep the Sun in the sky. Using your wind analogy, if a person is standing with his back pressed against a wall as a strong wind blows against the other side, the wind wraps around the wall, but the man feels little to no wind on him. If however, he were to start to walk away from the wall, he'll slowly feel a strengthening wind as he approaches the point where the wind, wrapping around the wall, will close in on itself, and he'll eventually reach a distance from the wall where the wind is at its usual strength. For the dark energy 'wind' this must be a point less than three thousand miles above the Earth's surface, as the Sun is affected the same amount by the dark energy as other celestial bodies are. But if dark energy does behave so much like a wind, there is no absolute barrier where dark energy does not affect a body on one side and it does on the other. It should be a gradual increase - this would make flight, and indeed space flight, considerably easier than on a Round Earth.