I believe that the dream was saying that Iron (Roman) and clay (Israel/Judah) would be intertwined, but that they would not mix, so to speak. They were together, but were totally different. Then, I believe that the church was the new kingdom, and it went throughout the world. I do not believe that we will stay here on earth forever, but we are established in Jesus now while we are here, but it is part of the kingdom of heaven that will last forever. I am not waiting for a thousand year reign here on earth. I think that this has most likely already happened, although I am not really sold on the idea that a thousand years just means a long time. I think that It probably means pretty close to a thousand years. Actually, the thousand year reign gets to me more than most of the prophecies, because I don't really understand when this did or will take place.
My understanding is that the 10 toes represent the European countries and they didn't mix very well either, they kept marrying one another but they never really united as one. Reason for the clay and iron to not mix together. But that is just my understanding of this prophecy.