Allergic to page three, eh? Well, I can sympathize with that.

The main question: what about out-of-combat casting? You basically have unlimited spell slots per day, since you can always slaughter an entire forest of squirrels--or something similar. Sure, not applicable in combat, but still potentially problematic.

The essence mechanic is interesting, if unusual. I'm not sure how the balance would work out, but it's certainly something that's worth fine-tuning.