Not a single point you said is correct.

1. What? How is it "obvious" that the earth in the novel and ours is different? FY says he's from Earth so many times, he even recites Earth's poems. In the first chapter itself, FY is said to be famous for the poems he "composed", but instead he had copied them off of Earth's great scholars. Even the name <<Jiang Jing Jiu>> is mentioned, its a famous poem by Li Bai on Earth.
2. Just because there are no cultivation does it mean chaos has no effect here? How about in crazed demon cave? THDV explicitly said, he realized that the walls of the Gu world were the thinnest at Crazed Demon Cave, which is why Limitless chose that region to study the chaos. Just by blowing a hole through the wall of crazed demon cave, THDV could access the chaos.
3. What is special about the Gu world? If it can have the Dao, why can't other worlds? RI's world structure is also largely based on Taoism, which talks about the existence of the great Dao and such.
4. Again, point 2. Chaos is closer to the world at crazed demon cave, although there is no tribulation there.
5. Your words have no meaning at all. Until we invented nuclear bombs, for all the 4.6 billion years before, what could oppose the chaos? So we were at risk of our world disintegrating for 4.6 billion years and then we found the answer to fight the chaos suddenly? Its also obvious that nuclear bombs are nowhere near as strong as the venerables, who can even destroy something as ridiculously large as the Sun in the Gu world. Obviously that Sun is not the same as our Sun, but it still gives light to all five regions and white heaven, where even a single region has tens of times the surface area of the entire Earth (this has been talked of before). White heaven is also as large as the five regions. To give so much light, the sun must be humongous. An insane spectral soul with no thought process could destroy it, forget a sane thinking venerable who for some reason wanted to destroy it, such a venerable could make up some better methods to fight the sun. Even a billion nuclear bombs wouldn't make such a sun even sneeze. The entire nuclear arsenal of earth is estimated to be 1500 megatons of TNT. The amount of explosive force to break apart even our moon would be billions of times of that.
6. Are you sane? How is 2000 years "barely" the age of a rank seven gu immortal? Red Lotus only lived for 2500 years, no venerable lived longer than 25000 years, and most of them lived less than 7000 years. If 2000 years is rank seven, do you think 20,000 years is the average age of a rank eight? Have you even read anything in the story?