Mr. Grave wanted the other members of the donner party to eat the flesh of his body once he died, so they could live. They were put into horrible conditions and their supplies were already run out weeks ago. To the group of pioneers it seemed that there was nothing to do for living but kannibalism, so they ate fleshes of the dead. Therefore, Mr. Grave was ready to make such a sacrifice, hoping that he can save lives.
The last one should be your answer.
Symbolism is an visible object representing an invisible object (ideas, ideology). Basic Grade 9 English. :)
Example
1. Apples tast
2. Books cover
3. Houses roofs
Answer: It basically means something can look beautiful on the outside but on the Inside, it can be mean and cold. Just like how people are.
Explanation: