I take it you are conceding the point about 25 miles being the correct distance to use then?
You cannot "see for yourself" the height, because there is no ruler marking height about sea level in the picture. You can estimate, which I did. Your estimate was on the extreme low end of what is reasonable, conveniently for you. Regardless of the fact, 14 feet at 25 miles, you STILL should expect to see a piece of the 300 foot cliff over the horizon. So even for the most conservative estimate possible, this does not, as you tried to imply, demonstrate the flatness of the earth.
Edit to add: Incidentally, the tide in that area varies by 7 meters or more, so well over 20 feet. So it's highly unlikely that the road is < 10 feet above the sea level at any given point. People don't typically build roads where they might flood.