Similar constitutional conflicts exist with the proposal and ratification of the reconstruction amendments. I agree that Lincoln's regard for the Constitution may have been as bad as any president in history. I'd stop short of saying he'd have eventually become a tyrant like Hitler, but I'm curious to know what you've read to leave you with such an impression. I think Lincoln was motivated to accomplish a noble goal by any means necessary, but ended up doing so in a less than noble manner. And some of his goals beyond ending slavery weren't very noble either, but I would still stop short of calling him one of the worst humans to ever walk the earth.
I've been reading history from that era recently as well and it's fascinating how much I learned in school that was totally opposite of reality.
Lincoln was definitely shady in terms of following the constitution. He disregarded numerous civil liberties and civil rights in an ends-justify-the-means way. Just as you say. But the Union won the war and were able to write the history books to make it look better than it was. There certainly is a lot more to the war than what children are told in school.
I started reading Jefferson Davis' The Rise and Fall of the Confederate Government. You have to remember the source when taking some of his arguments into account, but he backs all nearly everything with citations to letters, speeches, laws, and historical records.
What I found quite interesting was that the New England states, led by Massachusetts, heavily considered secession in 1803-04 because they were concerned with their loss of power over the Louisiana purchase. Furthermore, John Q. Adams wrote that he believed secession was a right of all states of the union. Apparently in the early 1800s no one actually thought that the decision to join the union was permanent. Rather, they believed that a state's membership in the federal government was contingent on the consent of the governed. That if those in the state, the governed, decided that they no longer wishes to remain in the union they were perfectly free to withdraw their consent and remove themselves from the union.
It is a fascinating book which I highly recommend reading. Jefferson Davis was an extremely well respected statesman who very clearly outlines the legal and factual history of the confederacy with documented sources.
In regards to WVa, you're probably right. It likely was unconstitutionally formed. But at this point it's too late to do anything about it. Five individuals seem to have more power than all of the rest of the nation combined.