It's best to have different questions in different threads. I'm going to answer the first one and hope you will start a new thread with the second question.
First, realize that lyrics are often ungrammatical, illogical, and even completley nonsensical.
Other times, the grammar is more-or-less right, but the sentence might be in an unusual order to make it fit the rhythm of the song.
Usual order: I need [something].
Unusual order: Something I need from you.
Now, replace "something" with "Everything that I need."
Translation: You are the only thing in this world that I need. There is nothing that I need that I don't get from you.