Here "you" is singular and refers to Jacob. But the blessing would also apply to Jacob's descendants. (See: [[rc://en/ta/man/translate/figs-you]] and [[rc://en/ta/man/translate/figs-synecdoche]])
"Dew" is drops of water that form on the plants during the night. This can be made explicit in the translation. AT: "night mist from heaven to water your crops" (See: [[rc://en/ta/man/translate/figs-explicit]])
Having fertile land is spoken of as if the earth were fat or rich. AT: "good soil for producing crops" (See: [[rc://en/ta/man/translate/figs-metaphor]])