Image that Enton plus Lightning sword with each clone. Then S/T teleportation. Sasuke is a bit too OP now.
1. Kage Bunshins disperse if they get hit hard enough. Naruto's clones can contest to that.
2. Sharingan still wouldn't help, there's a reason Madara barely used Kage Bunshins. It isn't efficient given Sasuke's arsenal.He has the speed and power. Bunshin feints are to set up attacks. There's no need seeing how Sasuke's justu usually have no prep-time.
3. Itachi's clones were different, unlike others.
4. It would be useful, but it isn't necessary for someone like Sasuke.
But if you want Sasuke to spam Kage Bunshins then by all means.
1 - It depends upon their stamina.
2 - Madara never knew Kage Bunshins till the end of his career. They were invented by Tobirama. His mastery over them is highly questionable, when Tobirama couldn't maintain more than one clone himself while he moved.
3 - Itachi clones are very similar to Kage Bunshins.
4 - Necessary? No. Useful for tricks? Yes. Given how clever Sasuke is, I can't see how they cannot be.
Also, did you actually state above that Sasuke would be in trouble Chakra wise if he used KBs? You can't be serious. When 1) he has half of Hogoromo's chakra, 2) his CC is at the Sage's level, 3) his chakra is extremely powerful and 5) he is already shifting dimensions with no repercussions. But KBs break his back? Yeah, okay.