You wrote a lot to meaningfully say nothing.
Yes, we all know why he made his choice to be the demon lord and what his theory is. I didn't say: "I don't understand why he chose to be a demon lord and therefore should stop".
I'm saying it would be much more meaningful to stop trying to be the enemy of the world, and instead look for solutions. The base idea that: "human society is inherently, in its nature, corrupt, so literally the only viable solution to mend society is by forcing them to fight someone bigger than themselves" to begin with, made no sense, but at this point in time, it's even more so.
He's a sage of magic, who also has a research team under his command, he could solve the issue of feudalistic society without having to be something as simple as a warlord: introduce new technologies, advances in medicine and surgery...Make the people's lives easier and safer under his rule. Expand with that ideology in mind, and rule the world via technological advances and commerce. If anyone tries to attack him to maintain their position, he curbstumps them with his armies.
TLDR: The MC has all the resources in the world to make smarter decisions in how he can actually fix the world, instead of being an entity that paints a mark on his back for all eternity.
But I also think it'd be a touch more interesting, if he'd admit he really is a vengeful spirit, with a big bias towards violence, everything considered, but his identity as Dwight balances it out with some level of rationalization.