These two occurrences of "he" refer to David, but they also refer to David's soldiers who helped David do these things. (See: [[rc://en/ta/man/translate/figs-synecdoche]])
# forced them to work with saws and iron picks and axes
These terms describe difficult manual labor that the defeated people were forced to do.
The people are referred to by their city. Alternate translation: "David required all the peoples of the cities" (See: [[rc://en/ta/man/translate/figs-metonymy]])