It's true that "double negatives resolve to positive". You can try to understand such sentences by changing each negative into positive one by one:
不能->能 没有->有 不能没有事做=一定要有事做( so you can see, 不能没有 is actually quite a definitive tone so i use 一定here to replace it) So you can translate it into "there has to be something to do".
没有->有 受不了->受得了 没有事情做受不了->有事情做受得了 which means "I cannot tolerate it if there's nothing to do."
Both sentences have the same meaning, but just put in different ways.
Maybe you can understand if i give you following examples:
a. People must have someone to love.
If you want to say it in the way "不能没有事做”,then you can say "People cannot have no someone to love", however, i guess nobody say it like this, so we can conclude that in this situation, you cannot directly translate it into English; instead you have to express it with a definitive word "must" to replace "cannot...no"
b. People cannot live without loving someone.
This is similar to the sentence “没有事做受不了”
