#3 No; "would" is conditional: "If I took the exam now, I would fail."
This means you are not planning to take the exam now.
We use "will" for uncertain things, and opinions about the future:
Maybe it will rain this afternoon.
I don't think I'll pass the exam.
You'll definitely pass the exam! Don't worry!
And we use "will" for spontaneous things (not planned a long time before):
It looks like rain. I'll take my umbrella.
(= I just thought of that idea, now.)