Here "now" does not mean "at this moment," but is used to draw attention to the important point that follows.
# may the promise that you made concerning your servant and his family be established forever
This can be stated in active form. AT: "may you do what you promised to me and my family, and may your promise never change" (See: [[rc://en/ta/man/translate/figs-activepassive]])
# your servant and his family
David is speaking about himself in the third person. This can be stated in the first person. AT: "me and my family" (See: [[rc://en/ta/man/translate/figs-123person]])
# May your name
Here "name" represents Yahweh's reputation. (See: [[rc://en/ta/man/translate/figs-metonymy]])
# the house of me, David, your servant
Here "house" represents family. AT: "my family" (See: [[rc://en/ta/man/translate/figs-metonymy]])