You're being too literal with your soul metaphor translations, I think that's the problem you're having.
For example, his Wisdom Soul might be an effete, effeminate scholar who carefully and meticulously studies fear. Or they might be the Scarecrow, using fear gas to study human psychology. They might be a living nightmare that possesses someone as their host. From how you describe him, he understands that his nature is fear (even in a base, animalistic way), so his understanding of his nature will be someone who understands or exemplifies fear in some way.
Hell, they might even be a little worm that lives in his head and controls him, his fear puppeting him and guiding him, a demon lord who controls his prince and must hide this from the law of Cecelyne.