1- why was it necessary to finish their job that night?
complete
the big man was attacked by the spiders that................................

it necessary to finish their job that night because they would break thorough the wall so they they have no chance or they would be discovered

because the team of archaeologist would complete their work at the morning 1
biting him 2

Im not sure !!

.Because the Egyptian archaeologists would come tomorrow and thy might discover the other rooms before the robbers
.Or / In order to discover the other rooms and treasures before the archaeologists

.bit him severely