If there's anything DT has trained me to do, it's speed-read while navigating through platforming hell.
Subcon is fun to interpret, so here's my take:
Aside from the obvious letters that spell out F
R
E
EDO
M, the "subconscious" part is just about who you think is responsible for what manifestations, and what that represents. For example, the spike wall can represent the heroes running out of time, or the Warmaster's
inability to turn back at this stage of Hex's plan
. Or it could follow the standard dream interpretation of running away from part of oneself, in either Jerry or Claire, or both, or maybe even Jeremy. You could argue that he's not really "there," but it's a fun option.
I think the most obvious interpretation is the airship. The heroes would see it as a sinister weapon that needs to be brought down, but here, its representation is a more innocent Mario incarnation, showing that the Warmaster considers it a tool of peace, and something that belongs in his vision for the world (which, here, is also represented by Mario graphics). The spike wall, on the other hand, is very out of place.
The "castle" in the last section is... well, this goes into "don't read unless you've seen the whole game" territory, so: