Just fyi...Here's a guy who shines a spotlight on a flat table but creates calculations that show it to be a globe.

No, he fabricates calculations with incorrect numbers and incorrect math.

He also limits it to small angles.

What he actually ends up with is a model which poorly matches (i.e. has large error) with both a flat and round table.

He also blatantly lies about what the flat table model would produce, claiming it would be 30 cm for one nail and 40 cm for another, when in reality the range is more like 28-30 cm.

It still completely ignore the measurements where a FE massively fails, that near sunrise and sunset, where the angle of elevation of the sun is close to 0, sometimes being negative as seen with clouds being illuminated from below and objects casting shadows upwards.

If you were doing that with a lens, you would need the lens at a similar height as you, being below you in the case of a negative angle of elevation.

And of course it needs to use a completely invalid model.

Refractive index varies monotonically with density for air. That means the lower the density of the air, the lower the refractive index.

As more dense air will sink, this creates a gradient across the atmosphere where the density drops the higher you go and thus the refractive index drops the higher you go.

This means refraction will result in light bending downwards, not up as you need it to to make your FE fantasies work.