The word "faithfulness" is an abstract noun that can be stated as "faithfully loving." Alternate translation: "I will never stop faithfully loving him as I stopped loving Saul" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
If in [2 Samuel 7:8-9](./08.md) you translated the direct quotations as indirect quotation, then here you may need to translate "you" as "David" or "him" or "his" as in the UDB. Alternate translation: "from before David. David's house ... before him. His throne" (See: [[rc://en/ta/man/translate/figs-quotations]])