Please note that the concept of the horizon in perspective isn't the earth. Although the earth might ascend to meet the horizon in the distance, the horizon is not the earth.
I'm interested by this, can you explain this further? Are you saying that the earth extends further than the horizon but you can't see it? I'm not clear how that can be when you get such a sharp horizon line on a clear day.
The horizon can be anywhere around you, and is not defined by the surface of an object. The horizon is the area where the perspective lines meet. If there were a skyscraper that was infinitely high, looking up from the base of the skyscraper would also create the effect of the perspective lines merging to a point. You would be looking at the skyscraper's horizon. If the skyscraper were not there, that horizon would still exist. It is just the area where the lines meet.
I see. Well, no it isn't. The horizon is simply where the earth meets the sky.
To be honest, I don't know what a horizon would look like on a flat earth.
On a globe it's a sharp line when looking out to sea because the earth curves away from you. Look along the edge of a ball - sharp line where the surface curves away from you.
That's why the horizon is further away when you get higher and the horizon line dips further below eye level with height.
These are observable and measurable and prove we live on a globe.
I guess a good way to prove that the horizon is not just where perspective lines meet would be to sail two ships maybe a mile or two apart away from you. Before they dip over the horizon they should still be a noticeable distance apart. This is an experiment you could probably organise as you live near the ocean.
If perspective points met at the horizon then the horizon would be a dot, not a line. If the horizon is what you say then why do only the horizontal lines meet and not the vertical? Do you actually think that horizontal perspective lines work differently to vertical perspective lines?
To respond to your other points:
All zoom does is make things bigger. So if a ship is truly half sunken then no amount of zoom will restore it. If the ship is not over the horizon but it's simply too far to see distinctly then optical zoom will make it clearer, that's all optical zoom does. It's not about "unmerging" perspective lines. They aren't merged in the first place any more than distant train tracks are merged. It's just that the limitations of your eye makes them harder to distinguish.
Once more: Shadow length and angle are determined by the PHYSICAL relationship between the light source and object. Not your or anyone else's perspective. Otherwise in your "row of lamps" thought experiment I as an observer from the side would see the shadow cast downwards as I can see the light is physically above your hand, you with your raised hand would see it cast upwards because of your perspective. That is not what is observed. The shadow is cast downwards for both people.
Again, do an experiment with a torch in a dark room. The only way you can cast long shadows is if the torch is PHYSICALLY near the ground.
At a distance of 6000 miles you are seriously suggestion that a gap of THREE THOUSAND MILES can't be seen?
For the beach to be obscured by waves then a close wave would simply have to be taller in apparent size than the people on the beach's apparent size. And I think we both agree that things get smaller with distance. As you keep saying, a dime can hide an elephant. But the only way a dime can hide an elephant if you're looking at ground level is the dime to be VERY close and the elephant far away. So actually closer waves are more likely to hide the distant beach than ones on the horizon which will be too small to discern - that's why the horizon at sea looks flat, yes there are waves but they are too small at that distance to notice.
So if you're 20 inches above the water then close waves are pretty likely to block distant beach or building unless you're higher than them - the video posted of the distant building being hidden by the curve of the earth was clearly done from above the waves level.
I've yet to see documentary proof of your experiment. You don't take "this is what I observed" as good enough evidence from anyone else (apart from Rowbotham, strangely, who as I may have mentioned thought the moon was translucent which some would think invalidates his other "proofs".