# My son will not go down with you

"My son, Benjamin, will not go with you to Egypt"

# with you

Here "you" is plural and refers to Jacob's older sons.

# For his brother is dead and he alone is left

"For my wife, Rachel, only had two children. Joseph is dead and Benjamin is the only one left"

# on the road in which you go

"while you a traveling to Egypt and back" or "while you are away." Here "road" stands for traveling.

# then you will bring down my gray hair with sorrow to Sheol

"then you will cause me, an old man, to die of sorrow"