None of that has anything to do with the justification of whether or not Preserving the Union, trumps the violating of the Constitution and the rule of law. Your conclusion that Lincoln was a great President, therefore what he did is right, is a wrong headed evaluation. It does not follow any rule of geometric logic. It is a bait and switch argument.
Now for a return question. What is so holy about the 50 states remaining as one Country?
Why couldn't there be say maybe 4 countries of 12 to 13 states each repersenting different geographical areas of our present country and not get along just as well? What would be wrong with that?
Why does what goes on in California have anything to do with what is going on in Florida or Maine? I have heard all the arguments about national defence and economy and such. But as a practical matter each geography area, having its own seperate government, would better represent the people. Each region would still be as powerful politically, economically and militarily, as most countries of the world including the European nations. The only exceptions to that would be Russia and China.
I do admit that being one nation has it advantages as far as logistics. But do those advantages override the right of the people to rule themselves?