Here are the sentences with a bit of explanation that should clarify what they mean.
The horse raced past the barn fell.
The horse (that was) raced past the barn fell (down). [But see note 1 below.]
The man who hunts ducks out on weekends.
What does the man who hunts do on weekends?
He ducks out on weekends.
The cotton clothing is usually made of grows in Mississippi.
Where do they grow the cotton that that clothing is usually made of?
They grow it in Mississippi.
The prime number few.
The mediocre number many; the prime number few.
Fat people eat accumulates.
The fat that people eat accumulates.
The tycoon sold the offshore oil tracts for a lot of money
wanted to kill JR.
Which tycoon wanted to kill JR?
The one who was sold the offshore oil tracts for a lot of money. Also, see note 2 below.
Note 1: When this was posted in rec.arts.books, Fiona Webster pointed out a quite different reading.
“As a long-time reader of horror literature, I have a different take on this: “fell” as an adjective. I’ve even seen it, in pseudoarchaic writing, following the noun. So then we would have the horse racing past a barn that is very dark and sinister-looking, perhaps filled with instruments of torture…”
Note 2: Morris Keesan pointed out an alternate reading.
“The tycoon sold the offshore oil tracts for a lot of money, and this money was wanted for the purpose of killing JR. (Perhaps the tycoon was going to drown JR in a huge vat of coins resembling the vault which Scrooge McDuck swam in. I think it more likely that a lot of money was wanted to hire a hitman.)”