Ken, interesting aspects. The meeting need not have taken place directly before the Golden Crown scene, but may well be a distant memory. "Last ride" referring to sex long ago, or to both scenes as a double entendre? Possible, but not too convincing.

What seems clear to me from the last verse is that at that time
a) the lady is lonely and quite willing to revive the old relationship that started before Casey's marriage
b) Casey has a family of his own, i.e. a wife and at least one child,
c) Casey visits her, but - sex or not - is obviously not enjoying himself (- why else would she desperately try to encourage him, even appealing for his pity?). Bad conscience, or lost erotic interest, or probably both. Therefore, the encounter cannot compare all that positively to his marital life.

We still need good explanations of the title, the "chain" (physical metaphor), and the "stumbling" etc.