Because the land masses are shrunk in the northern hemisphere and exaggerated in the Southern Hemisphere on a globe (which the most used flat map is derived from) I don't think they should be used for these calculations.

You seem logical. Do you understand the difference between the curvature and horizon regarding things that seemingly disappear in the distance? For example, if your target is compeltely behind curvature you cannot zoom in to see it. conversely, if your target goes behind your horizon, you can zoom in and bring it back into your view. I think this is the most common misconception that most people fail to understand.

Yes. This is why I asked in another comment for you to provide examples of e.g. the bottom half of the Moon being brought back by zooming in on it, or a mostly-hidden skyline, or a large ship (not a boat, too small, can be hidden by waves...) like an ocean liner.

Can you?