here's another thing that blows up your theory.
the moon is a bowl, with its concave portion facing us?
a crescent moon occurs when the sunlight strikes the lip of the cup opposite the location of the sun?
then in this picture, taken at sunset, the sun is actually directly overhead.
it's noon. but it's sunset.
the sun is below the horizon. but for your model to work, it has to be directly overhead.
oops
the moon is a bowl, with its concave portion facing us?
a crescent moon occurs when the sunlight strikes the lip of the cup opposite the location of the sun?
then in this picture, taken at sunset, the sun is actually directly overhead.
it's noon. but it's sunset.
the sun is below the horizon. but for your model to work, it has to be directly overhead.
oops