At the end of the day, I think the one single proof of FE or Ball E, will be the irrefutable circumnavigation of Antarctica. As it is, we have no modern attempt. We have no attempt to travel across its middle, and no one wants to take on the challenge of a North South circumnavigation of the planet, the last great achievement (which is odd to me). All three of these things Not being done are Very strange indeed.
In general, we at the Flat Earth Society do not lend much credibility to photographic evidence. It is too easily manipulated and altered. Many of the videos posted here to "prove a round earth" by showing curvature will show no curvature or even concave curvature at parts. The sources are so inaccurate it's difficult to build an argument on them in either case. Furthermore, barrel distortion and other quirks of modern cameras will cause a picture to distort in ways which may not be immediately obvious or apparent, especially without references within the picture. Photographs are also prone to distortion when taken through the bent glass of a pressurized cabin as well as atmospheric conditions on the outside. With this litany of problems, it's easy to see why photographic evidence is not to be trusted.
The Flat Earth model, however, places the sun and moon inside the glass dome. They are small and close, circling around and above the flat earth, creating day and night, and dividing day and night, light from darkness. The Flat Earth model is clearly described in Genesis 1:14-18. God makes it clear how God created the earth, the sky, and the sun and moon and where he put them. The Bible points us to truth and reality. The true Flat Earth points us to the Bible and Who created us.
3) The natural physics of water is to find and maintain its level. If Earth were a giant spinning sphere tilting and hurling through space then truly flat, consistently level surfaces would not exist here. There would be a massive bulge of water in the oceans because of the curvature of the earth. If earth was curved and spinning the oceans of water would be flowing down to level and covering land. Some rivers would be impossibly flowing uphill. There would massive water chaos and flooding! What we would see and experience would be vastly different! But since Earth is in fact an extended flat plane, this fundamental physical property of fluids finding and remaining level is consistent with experience and common sense. The water remains flat because the earth is flat!