I would argue that Jeff Davis & his ilk are the ones that wrecked the Constitution, and that Abe was the one who rescued it - although with changes required to maintain the security & order we depend on today.
Nope. It can be argued (and was actually in West Point text books before the Civil War) that the several States had the right to secede from the Union.
Lincoln mangled the Constituion to save the Union and created the Imperial Federal Government in the process.