1)
Why did Hashem need to arouse him?
1.
Radak: This was due to the afflicters, who wanted to stop the work. Hashem needed to strengthen their hearts.
2.
Malbim: He aroused also a Ru'ach of Gevurah and Yir'as Hashem.
2)
What Melachah did they do?
1.
Rashi: They began to quarry rocks and saw wood.
