Early Church Fathers on the Church being the Kingdom of Heaven

The Early Church Fathers on various topics: This was a 3700 hour project which included going through 22896 pages of the 38 volume set called Ante Nicene, Nicene, Post Nicene Fathers. I compiled 255 pages of quotes showing that the Early Church was always and completely Catholic. All of these quotes can be verified and found from the source which is free online.

Daniel 2:44-45“In the time of those kings, the God of heaven will set up a kingdom that will never be destroyed, nor will it be left to another people. It will crush all those kingdoms and bring them to an end, but it will itself endure forever. 45 This is the meaning of the vision of the rock cut out of a mountain, but not by human hands—a rock that broke the iron, the bronze, the clay, the silver and the gold to pieces. (kingdom would come in the time of the other kings in the vision and his kingdom would crush the others Church fulfills it)
Victorinus Commentary on the Apocalypse of John (240-303 ad)
For the kingdom of Christ is now eternal in the saints, although the glory of the saints shall be manifested after the resurrection.
Victorinus Commentary on the Apocalypse of the Blessed John ch 11 (240-303 ad)
8. "And their dead bodies shall lie in the streets of the great city, which spiritually is called Sodom and Egypt." But He calls Jerusalem Sodom and Egypt, since it had become the heaping up of the persecuting people.
Victorinus Commentary on the Apocalypse of the Blessed John ch 20 (240-303 ad)
1-3. "And I saw an angel come down from heaven, having the key of the abyss, and a chain in his hand. And he held the dragon, that old serpent, which is called the Devil and Satan, and bound him for a thousand years, and cast him into the abyss, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be finished: after this he must be loosed a little season." Those years wherein Satan is bound are in the first advent of Christ, even to the end of the age; and they are called a thousand, according to that mode of speaking, wherein a part is signified by the whole, just as is that passage, "the word which He commanded for a thousand generations," although they are not a thousand.
"He shut the door upon him," it is said, that is, he forbade and restrained his seducing those who belong to Christ. Moreover, he put a seal upon him, because it is hidden who belong to the side of the devil, and who to that of Christ. For we know not of those who seem to stand whether they shall not fall, and of those who are down it is uncertain whether they may rise. [R] [+] Moreover, that he says that he is bound and shut up, that he may not seduce the nations, the nations signify the Church, seeing that of them it itself is formed, and which being seduced, he previously held until, he says, the thousand years should be completed, that is, what is left of the sixth day, to wit, of the sixth age, which subsists for a thousand years; after this he must be loosed for a little season. The little season signifies three years and six months, in which with all his power the devil will avenge himself trader Antichrist against the Church.
Ambrose of Milan On the Christian Faith book 5 ch 7.150 (340-397 ad)
It is a good thing to be in the kingdom of Christ, so that Christ may be with us; as He Himself says: "Lo I am with you always, even unto the end of the world."
Ambrose of Milan On the Christian Faith book 5 ch 7 (340-397 ad)
Here we are the kingdom of Christ, and in Christ's kingdom. Hereafter we shall be in the kingdom of God, where the Trinity will reign together.
John Chysostom Homily 83 on the Gospel of John (347-407 ad)
"If My Kingdom were of this world, then would My servants fight, that I should not be delivered to the Jews." He undoeth that which Pilate for a while had feared, namely, the suspicion of seizing kingly power, "Is then His kingdom not of this world also?" Certainly it is. "How then saith He it 'is not'?" Not because He doth not rule here, but because He hath his empire from above, and because it is not human, but far greater than this and more splendid.
Augustine of Hippo tractate 115 (354-430 ad)
He saith not, "But now is my kingdom not" here, but, "is not from hence." For His kingdom is here until the end of the world, having tares intermingled therewith until the harvest; for the harvest is the end of the world, when the reapers, that is to say, the angels, shall come and gather out of His kingdom everything that offendeth; which certainly would not be done, were it not that His kingdom is here. But still it is not from hence; for it only sojourns as a stranger in the world: because He says to His kingdom, "Ye are not of the world, but I have chosen you out of the world." They were therefore of the world, so long as they were not His kingdom, but belonged to the prince of this world.

Augustine of Hippo City of God book XX ch 9 [354- 430ad]

But while the devil is bound, the saints reign with Christ during the same thousand years, understood in the same way, that is, of the time of His first coming. For, leaving out of account that kingdom concerning which He shall say in the e...nd, "Come, ye blessed of my Father, take possession of the kingdom prepared for you," the Church could not now be called His kingdom or the kingdom of heaven unless His saints were even now reigning with Him…..
And from the Church those reapers shall gather out the tares which He suffered to grow with the wheat till the harvest, as He explains in the words "The harvest is the end of the world; and the reapers are the angels. As therefore the tares are gathered together and burned with fire, so shall it be in the end of the world. The Son of man shall send His angels, and they shall gather out of His kingdom all offenses." Can He mean out of that kingdom in which are no offenses? Then it must be out of His present kingdom, the Church, that they are gathered. So He says, "He that breaketh one of the least of these commandments, and teacheth men so, shall be called least in the kingdom of heaven: but he that doeth and teacheth thus shall be called great in the kingdom of heaven." He speaks of both as being in the kingdom of heaven, (Teaching about the Church being the kingdom of God and the amillenial view of eschatology)

Augustine Reply to Faustus the Manichean Book 4 par 2 (354-430 ad)
These things you do not understand, because, as the prophet said, instructed in the kingdom of heaven, -- that is, in the true Catholic Church of Christ.
Augustine On Holy Virginity par 24 (354-430 ad)
For, although at times the Church, even that which is at this time, is called the kingdom of heaven; certainly it is so called for this end, because it is being gathered together for a future and eternal life