No, that's mostly wrong, and you completely failed to explain the blue sky or sunrise/sunset, there are no density differences in play there.Mr. Tweedy wrote:"Ever see a star twinkle? Lights refract above a campfire? Pavement that looks wet in summer but isn't? Wonder why you can see blue sky, or even light at all when the sun is below the horizon?"
In each of those examples light is moving between atmospheric regions with different densities, which have different refractive properties. In general, light moves in a straight line through an atmosphere. You don't see headlights twinkling on the highway or the light from your monitor breaking into the spectrum on its way to your eyes. This is because in general there are no extreme differences in density between regions of an atmosphere. Light only bends when it transitions between mediums; there is no medium that bends light in and of itself.
As for your no-twinkle examples, the lights DO "twinkle", it's just that our eyes cannot perceive it in many situations. (Nor is it a concern in typical applications/situations.)
Finally, there is no tangible medium that does NOT bend light in and of itself.
What's the speed of light in a vacuum? What's the speed of light in a air? Why are they different?
In those answers, you should begin to see the misconceptions you've posted.