Ryan, welcome to what feels sometimes like a rather small club! Let me take this opportunity to restate the argument.

The New Testament views the coming of the kingdom of God as an event in the foreseeable future (cf., eg., Matt. 16:28), that would have a decisive impact, first, on the present generation of Jews and, secondly, on the dominant hierarchies that opposed YHWH and his Christ and the degenerate pagan culture that sustained them. It amounts to an impending régime change for the people of God. What people encounter in the present of the Gospel narrative (healings, exorcisms, etc.) are not so much the in-breaking of he kingdom (though that is not altogether inappropriate) but signs of what God is about to do to transform the fortunes of his wayward people.

The coming of the kingdom of God will be accompanied not by global peace and justice but by peace and justice for the people of God in the place of political oppression and divine condemnation. They are a people facing the wrath of God: they lack peace, they have no ‘righteousness’ (cf. Daniel 9). This deliverance of the people, however, will have a global impact: the righteousness of God in acting on behalf of Israel, in keeping the promise to Abraham during this time of eschatological crisis, will be seen by the world - not least because emissaries will be sent out to announce what God has done, to proclaim this very ‘political’ good news.

So yes, in the contingent, historical sense envisaged by the New Testament, the kingdom has now come, broadly through the events of the war against Rome and the faithful defiance exhibited by the early communities as they faced up to the anti-Christian hostility of Rome. This is not to say that Constantine constituted the complete fulfilment of the positive hope. Constantine merely marked the point - actually and symbolically - at which the emerging community was finally vindicated in the ancient world and Roman paganism overthrown.

As you suggest, what we now look forward to - our ultimate hope - is not the establishment of the kingdom of God on earth (marked by a second coming of Jesus) but the renewal of creation. God’s reign over his people has come in the displacement of Caesar and the enthroning of Christ as Lord and king so that the descendants of Abraham through faith are now free to fulfil their vocation as God’s new creation in the world. We remain under that reign as long as there are still enemies that oppose God’s purposes - the last enemy being death. But in the end, once the last enemy has been destroyed, this kingdom will be handed back to the Father - it will become redundant (1 Cor. 15:24-28).

In the symbolism of Revelation the kingdom comes with the overthrow of Babylon the great and the vindication of those who suffered, who will reign with Christ for a thousand years (Revelation 20:4-6). But when the final justice comes, kingdom language disappears because there are no more enemies to challenge the sovereignty of God over his people. Instead, we have an account of a new creation: a new heaven and new earth and the new Jerusalem descending as a temple of the presence of the God who is worshipped and honoured by the nations of the earth (Revelation 21).