The 144k are first fruit Jews as you say. And who is a Jew?
Romans 2:29
But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.
Romans 10:12
For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him.
Do you believe Christ died on the cross for your sins? Do you obey his word and do it? Then you are a Jew.
Matt 13:39 says of the harvest:
The enemy that sowed them is the devil; the harvest is the end of the world; and the reapers are the angels.
Multiple verses in John tell us
the resurrection is on the last day! Not 7 years before the last day, not at the beginning of the end of the world before things happen, not before Christ leaves Heaven at the restoration of all things and not before his Kingdom comes.
Matthew 13:30 says,
Let both grow together until the harvest: and in the time of harvest I will say to the reapers, Gather ye together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.
Look what Christ says regarding it:
The harvest is the end of the world; and the reapers are the angels. 40As therefore the tares are gathered and burned in the fire; so shall it be in the end of this world. 41The Son of man shall send forth his angels, and they shall gather out of his kingdom all things that offend, and them which do iniquity; 42And shall cast them into a furnace of fire:
That implies Christ is reigning when they gather out of his Kingdom. For him to be reigning, as he is shown in Rev 14:14 as the son of Man wearing a crown, the kingdoms of the world are his. The implication is this event happens after the 7th trumpet is blown. He removes, in the millennial kingdom, all workers of iniquity. It's not after the millennium, It's in it. How does it end in Matt 13:43?
Then shall the righteous shine forth as the sun in the kingdom of their Father.
Do we shine forth as this in the millennial kingdom or is it after it? In it and after it. If we shall in it, why would this apply to only after it as you say? For the beast kingdom, it's citizenry and the man of sin are all thrown into the lake of fire before the 1 thousand years are finished. After the 1k years, all the dead, not in the book of life are thrown in as well. There is no harvest after the 1k years. There is only 1 harvest as Christ shows us at the end of the world. if there were another, he would have told us.