Of course God Knows would be the song Weiss and Ruby sing just before becoming the Official Couple. If one looks at the lyrics, Ruby was essentially making her Love Confession right then and there!
Siegmund's Jormungandr versus Siegfried's Balmung. The World Serpent against the Dragonslayer of Wrath. It makes complete sense that both weapons would be so opposed.
On a metaphorical level, Siegmund is Fafnir- he is incredibly tyrannical, dragon-like- to the point of breathing fire- and Siegfried 'slays' him to take Weiss home.
Jaune and Rook are not only linked in their roles (a Nice Guy who acts as the Love Interest to a skilled fighter with higher social standing), they even have contrasting Chess Motifs: Jaune's is the knight, one of the more strategic pieces on the board that jumps around to move, reflecting his nature as The Strategist while Rook's is the rook, a blunt piece that only goes in a straight line, reflecting his blunter, more practical nature as the Guile Hero.
How will the characters react to Penny, Pyrrha and Roman dying? They know full well alternate universes exist from the crossover with Lucina Reacts. The possibility that Pyrrha might die is not only not fiction to them, but an actual possibility that they were barely lucky to escape.