During Jack and Will's sword fight in the blacksmith shop, at one point Will improvised a weapon by grabbing a glowing rod from the forge. Sparrow, like anyone from a culture where smithery was common, would be aware that steel in that condition is too malleable to stand up against a cold blade; one hard stroke would cut right through it. Nonetheless, Jack appeared genuinely spooked. But there's an entirely feasible explanation for his response: the (very painful) experience of being branded has left Jack with a phobia of red-hot metal. Not that he panics at the very sight of it; he had no trouble handling a similar glowing rod to get the donkey moving. But when somebody is coming at him with such a thing, all Jack wants to do is get away.
Why did Jack want the cursed treasure so much when it's implied he knew it was cursed, or at least knew the rumours? Cursed or not, he was probably looking for a way out of his deal with Davy Jones, either by trading him the treasure or by hoping the curse would somehow make Jones unable to bind him to service.
When the cursed crew meets Elizabeth for the first time, they are genuinely afraid when she threatens to drop it in the ocean. Theatrically, it was to maintain the secret that they were cursed with immortality and unable to feel any form of sensation. It does appear confusing in hindsight as they could just jump overboard and get it back. However, it was a tense situation so they weren't really thinking straight, and considering the size of the medallion, it would have been like searching for a needle in a haystack at the bottom of the sea and would likely be taken by the current has she actually dropped it.
All those pirates captured at the end? They were hanged. Pintel and Ragetti only got prison because they were hanging around dressed as women during most of the final battle.
Barbossa cuts Elizabeth's hand slightly to get a "blood offering" from her. It is generally regarded as a humorous moment or as a proof that he has standards, but if they did succeed at lifting the curse at that moment, the pirates would've once again been able to enjoy carnal pleasures of life, with Elizabeth as the only woman around...
Sure, the scene where Ragetti gets a fork shot in his wooden eye (It Makes Sense in Context) is Played for Laughs, but fridge horror sets in if you realize that had that fork landed but a few inches to the other side of his face... he would have lost his last remaining eye and become a blind man.
However, lessened due to the nature of the pirates' immortality curse. Sure, he may be blind and in significant pain for some time, but as soon as he could step into the moonlight and exhibit his skeletal form, stepping back out of the moonlight would then heal any previously sustained injuries.
