What you wrote was very interesting and in fact, a new book out looks at the war not from the position of the South but from the position of the changes occurring in the North and how that affected the South rather than vice versa. Did the war "settle questions about the nature of the Union?" I would say, had no Constitution existed, that would certainly be a legitimate conclusion. However, the Constitution did exist and both sides predicated their actions upon it – the South correctly, the North in a facile, illegal and, frankly, mendacious way. When you have Lincoln and his ilk declaring that the federal government "created" the States, then you know that you are no longer dealing with an honest debate or honorable opponents.
Another book has been written which defines the differences between those who flocked to the war banner of the Union and those who did so on the part of the Confederacy. It is painfully obvious that the soldiers of the North told wives and family that they were subordinate in position to the need that the soldier felt to "defend the flag" and "preserve the Union" despite the fact that one had to be downright dull-witted not to know that a "union" is by its very nature is voluntary. Union at the point of a gun is conquest and, frankly, conquest was the nature of the Northern battle sentiment from the beginning. Indeed, long before the first shots were fired, Northerners on the whole had nothing but loathing and contempt for their so-called brethren in the South! Indeed, as early as 1812, the New England states wished to secede from any "union" that included the South! Sadly, the War of 1812 ended before that was accomplished.
On the other hand, Southern soldiers went to war primarily to protect their faith and families. The cause of the South and their mother states was considered one and the same as that of faith and family. Unlike their Northern counterparts, there was no need to "subordinate" anything of their lives in order to protect the South. Now, of course, it is possible that this viewpoint was predicated on the fact that the South was not the aggressor but was defending its land and people while Northern soldiery would be "making war" upon the land and people of other states (treason according to the Constitution).
Indeed, practically, the war did "settle the question of the nature of the union." On the other hand, as noted above, because the Constitution was supposedly in force, the question remains open because, in law, one cannot settle an issue by force of arms. So what we have today is the wretched result of the North’s "victory" – a federal government out of touch with "the People," disinterested in the "consent of the governed" and on a course of total economic and social destruction because it is no longer limited by the power of the sovereign states. One wonders if the Northern States could have seen the outcome of their foolish and treasonous assault upon their fellow Americans at the behest of an unconstitutional NATIONAL government if they might not have told Lincoln and his minions to go to hell! Remember, the sovereignty of the States of the South was not the ONLY state sovereignty destroyed in the War of Secession! When it was over, the States of the North were just as powerless as their