Some translations set each line of poetry farther to the right than the rest of the text to make it easier to read. The ULB does this with the poetry in 3:7-11,15, which are words from the Old Testament.
The author uses rhetorical questions as a way of warning his readers. Both he and the readers know the answers to the questions, and the writer knows that as the readers think about the answers to the questions, they will realize that they need to listen to God and obey him.