Answer:
The last one ("Peter is proud that he uses his brains rather than his brawn, and he would rather go hungry than settle for a manual labor job") is correct.
Step-by-step explanation:
"had missed many a meal rather than descend in the social scale" suggests that he thinks highly of himself and lowly of manual labor. He holds himself on higher standards and the previous sentences clarify his priortiizing of brains over brawn.