Time for some wall of text.
I concur, that the pace is too slow. I know it can't be helped, but it doesn't change the fact, that too much information and different characters are given and you already don't know, what happened and who they are, if it didn't happen or they didn't do something in the last 3 chapters. I'm not a big fan of politics and intrigues in mangas, if they get out of hand. "
Maoyuu Maou Yuusha" is a rare example, in which case it worked out.
If it gets boring or the plots are too stupid/naive/badly written, mention politics and cloak and dagger on the sidelines and leave them there, until you come up with something decent.
Though this manga doesn't have a bad/naive political setup, it's just the pace is killing it.
And yeah,
the attempted brainwashing was a dick move. Worthy enough to wipe out a whole organisation, kings family or threatening a whole country, just to make this point clear. Honestly, I can't remember who that king is, but creating a 100 meter tall wall around a whole city of his, darkening the sun for show and publicly demanding an apology for
everyone to hear or, well, be destroyed, wouldn't be to much to ask. But MC wants to keep a low profile, I guess. But why? Every major player knows of his existence, only the public doesn't. He isn't doing himself a favour.
A simple message:
If your king messes with me, I mess with you big time! You know, being Dark God and everything. Of course he wouldn't do something to the citizens, but even if they knew that,
no noble would dare to do something. And if they do, end them in a flashy way.
Also regarding the predecessors: I get the distinged feeling, one created the mage system and the other one the hero level system, because "OMG, IM ONA ISEKAIIII. WOOOOOHOOOOOOT!!!!!!!" and they messed the world up. MC should just remove both as they are unnecessary. And the monster tech. (Maybe keep the healing magic or level it up. If they want to use it to kill themselves in wars over and over again, it's there own fault.)