David asks this rhetorical question to tell Hushai that he will not be alone. This can be written as a statement. Alternate translation: "Zadok and Abiathar the priests will be there to help you." (See: [[rc://en/ta/man/translate/figs-rquestion]])
This is a generalization. It means all of the important and insightful things that he hears, not every single word he hears. (See: [[rc://en/ta/man/translate/figs-hyperbole]])