4. A governing system that was at best terrible- since it was confederal, rather than federal, there were many problems organizing troops, paying for the war, and even getting the troops to leave their states in some cases. Even if they had won the war, it wouldn't have been surprising if they broke apart later.
Bingo. The other three reasons you listed would have been hard to overcome, yes, but not insurmountable. There seems to be some sort of idea that if the Confederacy had managed to squeak by in the war, it would have lasted. Which is false. It would have been very hard for the Confederacy to stick together for much long without tearing itself apart. There was talk of Georgia seceding from the Richmond Government as early as
1861. Georgians and Texans would have been at the throats of the Virginians and South Carolinians in no time over the most trivial of details. The Confederacy lacked a unified government, and would have surely crumbled soon, if not by the 1870's.