Let's address some stuff regarding the vanishing point and horizons
Firstly, Light can be bent by gravity. However, Earth's gravity is RELATIVELY WEAK, compared to the sun and other bigger stars, and thus the bending of light is minimal.
Thus, at any point on the Earth, there will always be a vanishing point
Assuming that the Earth is flat, there will be NO VANISHING POINT. If you were to have perfect eyesight and are able to see infinitely far, you would be able to see many objects until your line of vision is blocked by an object. Thus, if you were to be floating out at sea, you would be able to see the nearest shore and building no matter how far you are away.
But, we can't
Assuming that the Earth is round, your line of sight would end at a certain point. This is true, and is the result of objects becoming smaller as they are further away from you. This effect is called micropsia. This proves the existence of a vanishing point and thus there can only be 1 explanation -- the earth is round