Congratulations on a very interesting piece of work, and on the courage to set out ideas on a topic that by its speculative nature will draw significant critique.
Very positive that you decided on a definition for "civilizational collapse", as this is broadly and loosely discussed without the associated use of common terminology and meaning.
A suggested further/side topic for work on civilizational collapse and consequences is more detailed work on the hothouse earth scenario (runaway cliamte change leading to 6C+ warming + ocean chemistry changes).
Compared to most of the scenarios discussed in this piece - the evolution of hothouse earth is a 30 - 200+ year process, rather than an event. In this context, ideas such as usable food stocks, living livestock, healthy seas etc.. are no longer valid.
In addition, the current models for warming by 2100 are in the order of 2.7 - 3.5C, without feedback effects. There is a significant body of debate that these levels are more than sufficient to trigger civilizational collapse, but only after cumulative emissions that are so high as to ensure the warming and its impacts continue, potentially also escalating to the hothouse scenario.
In any event, interested in collaboration on this topic, if this is of interest.