Questions about בראשית

Over the next few weeks I am going to post some of my questions about the Parsha. Note, as I have done in the past I am going to be focusing on internal questions not external questions.

My big question this week is how did Adam sin with the עץ הדעת if before eating from it he had no free will? How can a creature with no free will sin? The Rishonim (Ramban, Rambam, Rabenu Bechaye) give IMHO unconvincing answers. The Ramban and Rabenu Bechaye write that man was like a מלאך before the חטא and even so he sinned just like מלאכים sometimes do bad things. WADR, that makes little to no sense. If you have no free will then how can you choose to sin? One answer given by the Nefesh Hachaim is that before he ate from the עץ הדעת the yetzer hara was external. He had perfect clarity as to what was good and what was evil. After the חטא the yezter hara became part of man and now the yetzer hara can convince us/trick us into thinking good is bad and bad is good. The problem is that if he had perfect clarity why did he sin?

Additionally, we can ask that if man was like a מלאך with no free will then what was the point of creation? Hashem already had מלאכים why did he need man?

In truth the whole story makes very little sense. Chazal say that if Adam hadn't sinned and had made it until Shabbos the world would have fulfilled it's mission. and none of us would be here. Lets think about that. God creates the world with a certain outcome in mind and then Adam sins and upsets the applecart and everything changes from a to z. The world becomes a completely different place with new challenges and a new way of life. Why would an omniscient God do that? Why would he create a world one way and a few hours after the creation of man change the whole world? If God knew that man was going to sin why not just create the world that way? The same applies to the Mabul, why create the world and destroy it a thousand years later? Why not just start from Noach?