I'd like to suggest an approach to allegorical interpretation that I've used with individual students. Some of my students, too, struggle through Dante's "dark forest" and wonder why he wrote about a leopard when he apparently meant "malice and fraud." My suggestion is to start with a short Aesop's fable. Readers can see that certain animals (a dog in the manger) really stand for certain kinds of people (irascible folk who can't endure others' happiness). They see that one situation (grapes hanging from the vine just a mite out of reach) really means another (anything beyond one's grasp). With that introduction, Dante's writing may make more sense.