No you haven't. You admitted that even with your water level experiment you filled a bath said "the world is flat" and walked away.
You have no experiment and no evidence that proves the earth is flat and not spinning.
The 8 inch per square mile rule is not a rule, for a start. It is an approximation and is used to calculate the drop over the horizon. It gives a rough figure that gets more and more inaccurate the larger the distance. However you can only ever meaningfully calculate the drop for a quarter of the earth, using the approximation or the accurate formula.
If you picture yourself standing on top of a ball, and you have a target, as soon as that target moves more than a quarter of the way round it is on the underside of the ball or behind you. Ok you can turn around as it comes back, so you are never going to see it.
If you calculate the drop over the horizon of a distance of 24,000 miles, that is actually all the way round and back at your feet.
I graphed them out, ignore the blue line. Red is the real rule, green is the square rule, distances in km, not miles:
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You can see that because the real rule is essentially a cosine rule, once you travel the circumference of the planet the drop is back to zero. Meanwhile this square rule goes off into infinity.