The themes of dreams plus pirates mesh well, I like the idea to do this after a TPK.
I sense a missed opoortunity to use the five emotional stages of grief for the emotions of the crew. As the whole scenario is in itself quite railroady (waterway-roady :-D) one could lead the crew evary 1,2 stations a stage further, rewarding roleplaying into this. (This would need a lot more trigger warnings, though)
The mirror crew seems quite harsh, especially right before the boss? How is the system build? Is there healing between the stations?