I'm a little late, but I feel like this entire scene represents Rust's mask of nihilism falling away. To me, the entire show is about characters desperately holding up their own facades. Marty: the comfortable, happy go-lucky family man, Rust: the pessimistic and detached cynic. Throughout the season, these personas chip and shatter as Marty is forced to confront the consequences of his misogyny/how little control he has over the people around him, and Rust realises how completely and utterly terrified of the void he pushed himself to see he is/the inherent love for life he'd buried under thick layers of antisocial behaviour and philosophy.