Wait, what? Absolutely not. The Librarian is a Lifeworker, wich is above the Didact rate, Warrior-Servant. Both are lower in rank to the Miners and Builders.
The second part is unclear, you have to adjust your grammar. Prometheans were Forerunners, wich at the end of the war with the Flood were mutated into AI (immune to the infection), the Knights you fight in the game. When the didact realised his forces were not sufficient, he too composed humans into AI. So, the knights you fight in the game are both Forerunners and Humans.
San Shyuum were not Covenant. This is an alliance formed in the "after-array" galaxy.
Again, no. The Forerunners were not conscious about the existance of the Flood. They attached Humans because they thought they were invading their territory, instead of running safely away from the infection.
No. He didn't create the Composer, he just used it against humans to have a new army of Knights, and then he tried to use it on Earth to prevent the human supremacy of the galaxy. It doesn't disintegrate them, it turns them into AI.
Not at all. The Prophet asked the Dreadnought's oracle why there were so many Forerunners' artifacts on Human's planets, and the oracle (wich was a sliver of the original Mendicant Bias) said "his makers are his masters, he served his makers, his makers are the humans, he would conduct his makers safely to the ark." So, the Prophets kept this secret to not destroy the basis of the Covenant, and decided to genocide the Humans.
Ufff, please correct your grammar, i had to read it three times before i could get it.