What is Ralph's reaction when he encounters the pig's skull?
At first, Ralph is just puzzled when he sees the pig's skull.

Then, he becomes sick and uneasy and in rage, knocks the skull down, splitting it into 2 pieces. He takes the stick out of the ground to use as a possible weapon.

Driven by fear and hunger, Ralph manages to make contact with Samneric who are standing guard at Castle Rock. Of what do they warn him?
At Castle Rock, Samneric are standing guard. Ralph manages to make contact with them. They warn Ralph of Jack's plans to hunt and kill him.

In what ways does the tribe try to hunt down Ralph?
Jack and his tribe try to hunt Ralph in many ways. First, they send a boulder toward his hiding place. Then, they try to smoke Ralph out, by lighting the island on fire.
What or who saves Ralph in the end?
Fleeing from the fire, Jack, and his hunters, Ralph makes it to the beach, and is met by a naval officer. Jack and his hunters stop trying to attack Ralph when they see the officer, so that is what ultimately saves him.

However, he would not have ran to the beach if Jack had never lit the island on fire in the first place, so Jack doing that also ends up saving Ralph.

Definition:crackling sound
crepitation
Definition: ponderously clumsy
elephantine
Definition: magic spell; enchantment
glamour
Definition: unfriendly; hostile
inimical
Definition: obscured; blocked from view
eclipsed
Definition: intensely; painfully
excruciatingly