Jesus was sent only to the lost sheep of the house of Israel (Matthew 15:24) and Matthew was therefore written to the Circumcision, not to anyone else.  The “wheat” and “chaff” are simply figures used to differentiate the true Jewish believers in Christ, from their falsely Jewish counterparts. The Book of the Revelation, in Chapters 2 and 3 speaks of these counterfeits.

“I know thy works, and tribulation, and poverty, (but thou art rich) and I know the blasphemy of them which say they are Jews, and are not, but are the synagogue of Satan” (Revelation 2:9).

“Behold, I will make them of the synagogue of Satan, which say they are Jews, and are not, but do lie; behold, I will make them to come and worship before thy feet, and to know that I have loved thee” (Revelation 3:9).

Annihilation is a word and concept that is completely foreign to the Scriptures.  One can search all one likes and will never encounter either in any Bible, except for the New World Translation which is a (per)version exclusively doctored by and for the sect of  the Jehovah's Witnesses.  And the kind of annihilation that volume refers to is a complete change to nothingness, which is impossible.  All matter can only be reduced as far as its most basic state.  Chaff when burnt up, becomes ashes; therefore, burnt up chaff cannot be annihilated according to the JW definition of the word.

The “unquenchable fire” referred to in Matthew 3:12 and Luke 3:17, is the fire of the city of Jerusalem's rubbish dump, which shall again be brought back into being when Christ rules in his Millennial Kingdom in Israel.  The fires of this dump known in the Greek as geenna or Gehenna is where all those condemned to death shall be cast, not being deserving of a decent burial after their execution.  The fire is referred to as unquenchable only because it is maintained in a constant state of combusting. It is not a figurative reference to eternal torment.

Eternal Torment is but another church invention which came about due to mistranslating the Greek word Aion as "for ever and ever."

An Aion is a very long period of time, but the various Aions all have both a beginning and an end.  Some Aions are longer than others.

But the word Aion, mistranslated "for ever and ever" does not mean unending.  An easy way to see the truth in what's being written of here is the fact that, as Scripture states,  “God [shall] be all in all” (1Corinthians 15:28); Well, God cannot be “All in all” if either annihilation or eternal torment are true.  It would make Him “All in some.” All truly means all, not just some; and this understanding is but one of the many which point unmistakably to the truth of universal reconciliation.