I respect your right to believe what you choose. I do not find your evidence against a global deluge compelling. As mentioned previously, the global deluge was a unique event and bears as little resemblance to a local flood as a gentle breeze does to an F5 tornado. As to the dates given to ancient civilizations, I find this quote from a Bible encyclopedia pertinent: "With the Deluge great changes came, for example, the life span of humans dropped very rapidly. Some have suggested that prior to the Flood the waters above the expanse shielded out some of the harmful radiation and that, with the waters gone, cosmic radiation genetically harmful to man increased. However, the Bible is silent on the matter. Incidentally, any change in radiation would have altered the rate of formation of radioactive carbon-14 to such an extent as to invalidate all radiocarbon dates prior to the Flood.
With the sudden opening of the ‘springs of the watery deep’ and “the floodgates of the heavens,” untold billions of tons of water deluged the earth. (Ge 7:11) This may have caused tremendous changes in earth’s surface. The earth’s crust, which is relatively thin and varied in thickness, is stretched over a rather plastic mass thousands of kilometers in diameter. Hence, under the added weight of the water, there was likely a great shifting in the crust. In time new mountains evidently were thrust upward, old mountains rose to new heights, shallow sea basins were deepened, and new shorelines were established, with the result that now about 70 percent of the surface is covered with water. This shifting in the earth’s crust may account for many geologic phenomena, such as the raising of old coastlines to new heights. It has been estimated by some that water pressures alone were equal to “2 tons per square inch,” sufficient to fossilize fauna and flora quickly.—See The Biblical Flood and the Ice Epoch, by D. Patten, 1966, p. 62." (IT-1 p.609)