"You have more food than your wife."
Translation:Έχεις περισσότερο φαγητό από τη γυναίκα σου.
Why is the article accusative?
Because the preposition από requires the accusative case.
Surely the word 'έχει' is understood at the end
No. από is not a conjunction and can't introduce a phrase with a verb.
You could add a conjunction and have a sentence such as Έχεις περισσότερο φαγητό από ό,τι έχει η γυναίκα σου.
But those two sentences are about as different syntactically as "We were late because of him" and "We were late because he was late" -- you can't say "We were late because of he" and say that "was late" is understood: "of" is a preposition and cannot introduce a clause with a verb.