Here "bones" refers to the deepest inner being of a person. Alternate translation: "My whole inner being" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The implicit answer to this question is that no one is like Yahweh. Alternate translation: "Yahweh, there is no one like you ... those who try to rob them." (See: [[rc://en/ta/man/translate/figs-rquestion]])
The words "poor" and "needy" mean basically the same thing and emphasize that Yahweh saves many who need his help. (See: [[rc://en/ta/man/translate/figs-doublet]])