Lots of "looking back" in your dream makes me think that it's a Mercury Retrograde dream.
Buildings represent your mind -
"labyrinth funhouse college party" sounds like a stress dream. You're wandering through your mind, perhaps? That's a Mercury Retrograde thing.
The
guitar is a medium for communication (also resonating with Mercury? In alchemy Mercury symbolizes Water and the Soul.) You may be afraid that your ability to communicate is being inhibited by your tools.
Mercury's about to go into retrograde in Aquarius... leading us to the
fish that your ex gave you... your connection with your ex is alive, dead, alive, then unknown?
In alchemy,
Salt symbolizes the Body, the Earth but "Dream Moods dictionary" (I quote it because it's search-engine optimized!) sez this about salt -
Salt
To see salt in your dream, represents added flavor and a new found flare in the experience of life. You may be experiencing and elevated sense of individual worthiness and increased zest and vigor in your life. Your efforts are paying off. Alternatively, salt also symbolizes dependability, truth, dedication and longevity.
Depending upon which meaning resonates with you, being crushed by a salt staircase you're descending (into the earth) could be a warning to yourself that you shouldn't trust what seems dependable. Are you in poor health? Ecological danger where you live? Or it could be anxiety about crumbling infrastructure.