How are the remaining storylines resolved in the final chapter, and how are those resolutions linked thematically?

Monte Cristo's final act of divine justice is completed in this final chapter. He inflicted ultimate despair upon Maximilien, thus Maximilien is now deserving of ultimate bliss. Monte Cristo is also given a second chance at happiness with Haydee. It is significant that this chapter ends on the Isle of Monte Cristo. It symbolizes and marks the end of the Count's journey of vengeance. The journey had begun here when Dantes had dug up the treasure of Monte Cristo. The journey is now over, and Monte Cristo disappears into the horizon.