Taran needs protection to get the lid off of the pot in the beginning, but when Dallben does it, he has no protection. It must have been because of his training under the Witches of Morva.
During the climax, the Horned King's penultimate line "You… shall satisfy the Cauldron's hunger!" has a weird pause between "you" and "shall". Actually, it's likely the Horned King was going to insult Taran (You Fool! or other) but had the idea of feeding him to the Cauldron mid-sentence and changed the purpose of the "you".
As discussed on the YMMV page for They Wasted a Perfectly Good Plot, many people would have liked to see Taran fight the Horned King with Dyrnwyn. Except that those same people must remember, Taran never considered the idea that he would have to trade the sword for the Cauldron. He only assumed that it was something they could actually find in Morva and was intending to use the sword to destroy the Cauldron.
