Recurring motifs to weave in where they fit naturally — never forced:

Hands — competence, care, and guilt. Lena watches people's hands to read them; her own shake when she thinks no one is looking.

Cold and warmth — the failing reactor literalizes the crew's dwindling humanity. As the station gets colder, the small warmths the crew show each other matter more.

The airlock — every major turning point happens at or near an airlock: thresholds, choices, points of no return. The two-person rule (see tech rules) makes every crossing an act of trust.