Another problem with you theory occurred to me. In the video you linked about why the sun isn't visible to the entire flat plane earth, it's due to a refractive lens covering earth. However, if this is true, that refractive lens would also refract the light from the stars and other celestial objects in the sky. This means that they wouldn't produce clearly circular orbits in the night sky. It would also produce a lot of distortion in the sky near the horizon, at least from the refractive lens example shown in your video.