The word "precious" refers to how greatly the writer values Yahweh's covenant faithfulness. The abstract noun "faithfulness" can be translated as an adjective. AT: "I greatly value how you are faithful to your covenant" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
This does not mean that God has a house with food. This is a metaphor for abundant provision. AT: "as if they were eating the rich food from your house" or "with your rich blessings" (See: [[rc://en/ta/man/translate/figs-metaphor]])
There are two metaphors here. God's abundant blessings are spoken of as if they are the water in a flowing river. Also, those who receive those blessings are spoken of as if they are drinking them like water. AT: "your precious blessings are like a river from which you will let them drink" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "light" is a metaphor for true knowledge. AT: "when you enlighten us, we will know the truth" or "your light is what enables us to know the truth about you" (See: [[rc://en/ta/man/translate/figs-metaphor]])