What is the literal allusion for,"it was too late, for we had both wandered too far into a net of expectations and had left no crumbs behind."...

I assume you mean to say "literary allusion" rather than "literal allusion."  If so, the allusion in the quote you give is to the fairy tale "Hansel and Gretel."

In this fairy tale, the two siblings, Hansel and Gretel, are going to be left in the woods to die by their parents.  This is happening because their parents are too poor to feed them.  As their father leads them into the forest, Hansel leaves a trail of bread crumbs so that he and his sister will be able to find their way home.

This trail of bread crumbs is what your quote is alluding to.