I do think that changing “earth” to “Earth” – a common noun to a proper noun – is a significant change. “Let me be frank” isn’t the same as “Let me be Frank.” I could describe how during a dust storm “earth blew up,” but “Earth blew up” can only mean a rogue Death Star is on the loose.
The name of our planet, Earth, is a different word than “earth.” While “earth” has some overlap with the Hebrew word erets, “Earth” is foreign to it. For one thing, erets is about dry ground or land, whereas oceans are just as much a part of planet Earth as continents. If you translate erets as “Earth” in the flood account, you increase the contradictions: now even more verses state that the flood made an end of all flesh on the planet, not just on dry land. You’ve also increased the animals that need to be on the ark, since creeping things on planet Earth would include everything that creeps in the oceans. Obviously this is not what the text intends to communicate!
This is why translators tend to use “earth” uncapitalized, if they use that word at all. (One exception would be Genesis 1:10 where “God called the dry land Earth,” since this is a name. But it’s a name for dry land, not the planet.) I checked the translations I have in my Bible software, and The Message was the only one to use “Earth” aside from in names (e.g. Gen. 1:10; Isa. 54:5; Lam. 2:15; Rev. 17:5) or personifications (Job 16:18 in GNT; Exod. 15:12, Prov. 30:16 and Isa. 45:8 in YLT; Jer. 4:28 in DRB). What remains to be seen is if your 70 translations are any different.
Using lowercase-e “earth” is a deception? This is quite a change from earlier when you said, “I do not believe anything different to what the seventy Bible translations say.” Now, it appears you see yourself as qualified to correct their work.
If you truly believe lowercase-e “earth” is a deception, perhaps you should…
But first, please finish your investigation of just how many of them follow that deception of using a lowercase-e for earth. You identified the KJV. One down, sixty-nine to go!
That’s forcing a modern level of precision on texts that weren’t aiming for it, no different than asking if there are seeds smaller than mustard. In the Bible, “everywhere under heaven” refers to a wide area of land, such as all the nations around the Israelites who began to fear them (Deut. 2:25). I’m not going to call that verse in error if the dread didn’t spread to China or Antarctica. The expression basically means everywhere you can see, from horizon to horizon. It shouldn’t be pressed into being a scientific term.
There’s a quite similar phrasing after the flood. God tells Noah, “The fear and dread of you shall rest on every animal of the earth and on every bird of the air, on everything that creeps on the ground and on all the fish of the sea; into your hand they are delivered” (Gen. 9:2). Again, taking this as an absolute scientific statement just makes it wrong. The Galapagos Islands, for instance, are noted for how the animals don’t see humans as a threat. Other islands isolated from humans for millennia or more are similar. The dread of humans comes from many generations of interactions with humans; it wasn’t universally added to every kind after the flood. Just like rainbows, the flood account gives origin stories for things that scientifically have other explanations.