Good try,
G55, but as you correctly say, it isn't the right interpretation
I shall write comments on your interpretations, make out of it what you will
With the start, the first thing that I would have asked you would be whether you think Faramir's dream is unveiled by the skies. Maybe it is, if you were thinking along the lines that in that dream the sky in the east darkened and there came the voice speaking the riddle, of however it was. It could be that it was the skies that had spoken in that place, if it could be thus interpreted, then indeed it was a tale told by the skies that unveiled the truth about the Broken Sword etc. But like I said, it isn't the Broken Sword. I think you have proceeded correctly in the analysis of the second verse, especially in the analysis of why it isn't right
And as usual, I took good care of which words I have used. If there is a word, it isn't just random, it has its purpose there.
So, the door is open - continue guessing...