Sister nbegam,
Well I haven't done a deep research myself on the topic of whether the flood drowned the whole world or not, but I did read the researches of scholars on this topic and I agree more with those scholars who say that the whole world wasn't flooded, just the few people of Nuh PBUH.
Moreover, the Bible says the whole world was flooded and this is listed as some of the top mistakes in Biblical scriptures according to modern science, hence I agree with those scholars who read in context and with tafaseers that they explain that the whole world wasn't flooded but just the tribe of Nuh PBUH.
The Quran doesn't say "the whole world was flooded", I got to say this again, in context, the Quran doesn't talk about a worldly flood. In context it just talks about the people of Nuh.
So either way, it's up to you, I don't want to argue on this.
And regarding the 120,000 Prophets, see, you said Quran doesn't speak about it so you don't need to know them. Sister, the Quran also doesn't speak about 2+2=4. So does that mean you don't need 2+2=4 in your life? Lol.
The Quran is not a book of Science, SCIENCE, it's a book of signs, SIGNS. If the Quran had every knowledge, then it would be as big as the Burj Khalifa, which is not the case.
Please don't misunderstand, the Quran isn't a book of everything, it's a book of Signs, it is a book of Ayats, to know more about how to lead our daily life, the basic principles are given in the Hadith.
But the Quran also says to gain knowledge. This knowledge is both religious knowledge and worldly knowledge too. Please note!
So the part of Prophets not mentioned is pretty much like worldly knowledge. Same like how you study F=ma in Physics. It helps you lead your life, similarly this knowledge gives you some past experiences of Prophets which is "helpful" if you keep in mind.
Just because Allah didn't write in Quran doesn't mean you cannot learn it for "worldly knowledge".
I already said, F=ma is also not written in Quran. Does that mean using this formula is Haram? Lol.
Hence like I said, something agrees with Quran, we say it's true, something disagrees, we say it's false. Something neither agrees nor disagrees, we say it's ambiguous . And this knowledge which neither matches, nor contradicts, I tag it as "ambiguous" and there's nothing wrong if you learn about them, just like there's nothing wrong in learning F=ma.
And you asked if I have all knowledge of Quran to move to more researches, definitely not! I don't, even my next 25 generations won't. You cannot expect a person to understand everything of the Quran and Hadith even if he lives for 100 years. The most we can do is research and learn, which we do, and which the scholars of the past and present did and do, and scholars of the future will too Inshallah.
Hope this helps.