S'mon said:
Any usable advice welcome.
Okay, with the caveat that I think the adventure is best run as it is, here are some thoughts on how to pull it apart and run each pane separately from the whole:
A lot of the adventures can be run with very few changes to their set up. Have the party hired to perform a certain task, change the item the party needs to locate in order to exit the pane into a treasure/NPC/lost bit of knowledge or whatever that their patron needs.
Those that are bizarre and/or highly magical can, as has already been suggested, be magical traps the party is hurled into - perhaps they are exploring the manse of a crazed wizard or the like and such traps are dotted here and there. as the wizard feared he or an apprentice might get trapped in the weird dimensions accessed by the traps he left an item in each that would allow for a safe return.
Some of the panes have a mutual theme, being at sea for example, and with a little effort could be strung together as a series of encounters and adventures.
If you'd like to keep the basic set up but allow the party to turn down or fail in some panes, or go on other adventures in-between, then have the Mors be searching for the gemstones stolen from the Fairie Queen's necklace. Each has been scattered to the four winds by a rival deity who has put the blame on the Alfar trickster god. From time to time he appears to the party and requests that they pass through a pane that he conjures forth then and there and locate the gemstone (which of course will be the item required to leave the pane too). He mentions that the hero McGregtim has become lost trying to perform this quest and asks the adventurers to try and locate him during their explorations too.
To add a bit of difficulty then have Gwynn and Bili be the real perpetrators of the theft, you might have them send their own team of adventurers to stop the party both inside and outside of the various panes.
Just some thoughts, as I said the adventure will work best run the way it is written
Jon