"We the people of the United States in order to form a more perfect union..." Can you tell me why they included the word "form" there?
More perfect from what? That's Luis' point. It wasn't a new country as the United States already existed, and did so under the Articles of Confederation. And as I think everyone agrees, the purpose for many of the delegates was to improve the Articles, and it simply merged into a whole new constitution, because there were just too many changes. In any case, one late change to the preamble put in the words "We the people" as a change to "We the people of the states of, etc."
Why did every member of the N.Y delegation leave the convention (Hamilton alone later returned) when it became clear that they had no intention of working on the Articles of Confederation and were going to write a Constitution instead?
Only a fraction of the delegates stayed for the whole convention for a variety of reasons. But Hamilton was one of the strongest proponents of a new constitution. A few wouldn't even sign the document at the end. But I'm not sure that means anything.
Why are the words "perpetual union" nowhere to be found in the Constitution?
Well, since the Union already existed, the purpose as stated was to form a more perfect one. Those words simply show that it was a transition, first off to strengthen that Union and fix some issues involving state interactions. But it became obvious early on for a variety of reasons that there were simply too many issues to patch up the Articles.
What was the status of Rhode Island and North Carolina between the time the Constitution was ratified and the time they finally got around to ratifying it? Were they still governed by the articles of the Confederation, independent colonies again, or members union governed by the new Constitution despite the fact that they refused to ratify it?
Well they hadn't rejected the Articles of Confederation, and until they finally ratified the Constitution, would not have been governed by the Constitution. Still it was a relatively mute issue as I'm not aware of any conflicts resulting from it, just one more reason why the transition was principally aimed at a stronger government (more perfect) rather than the creation of a new Union. A reading of Anti-Federalist Papers is proof that the delegates were anything but united in there goals.
And lastly if if the Articles of Confederation bound states to a perpetual Union how is it that we are now governed by a completely new Constitution and the articles are history?
Asked and answered. And the USSC in
Texas v White confirmed that secession is unconstitutional.