So: A Thousand Miles.
The song could be about New York/Broadway, but let’s be honest, Rachel is singing to a star named Finn Hudson.
If I could fall into the sky Do you think time would/could pass us by? 'Cause you know I'd walk a thousand miles if I could see you If I could just hold you Tonight
If Rachel fell into the sky, she would fall into space, or towards Heaven (away from the Hell that she accurately labeled McKinley as). Time was Finn’s barely-controlled power and time dilation occurs during space travel.
Makin’ my way downtown Walkin’ fast, faces pass And I’m homebound
"What are you doing here?" "I’m home."
That’s how Glee was supposed to end. Rachel was supposed to succeed on Broadway and on television, walk away from fast-paced New York life, and go back to Finn back home, where he’d got a handle on the teaching and found personal fulfillment by himself. Winning separately would have meant the Finchel unit could be restored.
Corollary: Sue spends the episode trying to restore Klaine, who have taken the reins of the will-they-won’t-they, annoying-but-you-totally-love-it relationship drama in Finchel’s place.
Rachel is singing about Finn, but what about Sam? He’s hypnotized to be in love with Rachel even though his girl is Mercedes. By the previously established rules of how Glee (and most musicals with sufficient substance) operates, Sam losing control of his mind means that he’s not singing his true feelings.
Rachel falls in love, or back in love, over duets: it’s happened with Finn, Jesse, Kurt, Will, Mercedes, Blaine, Santana, and Quinn. It’s how she co-opts her newest sidekicks (Elliot) and makes it up with friends she’s insulted (Artie). So Sue hypnotizes Sam and causes him to sing the words that Rachel will fall in love. Sue makes Sam’s Rachel’s duet partner. She makes him channel Finn’s feelings. He echoes Rachel’s words, because Finn was just barely secondary to Rachel in the narrative, because he learned how to dream from her. Because Rachel Berry is a force of nature and therefore operates by rules, and Sue knows those rules. She is a character and a fan and a hater of Glee and she knows very well how her show was supposed to end.
This part is not sung in the episode:
It’s always times like these when I think of you and I wonder If you ever think of me
'Cause everything's so wrong when you don't belong Livin’ in your precious memory
Two things I can think of here: they don’t sing the lines where Sam/Finn admits that something is wrong or where Rachel mimics the boy without free will, instead of the boy without free will mimicking the sad, lonely, force of nature.
Mostly ow ow ow ow ow, but also whoa smart.