
You wrote a lot, but I will only comment on some things, I am not criticizing your opinion, just saying what I think about those topics.
First, the killing is reflective of the time and kind of society the story in which the story takes place, this a time and a society that has no regard for people's life, they only care when its a lot of people. Also he was previously a king so I think it's normal that for him it's more important to keep working towarda the future rather than worry about every single life, because it's impossible to save everyone. Furthermore, I think most times either someone dies because they did something worthy of dying (for the time's laws I mean, because law used to be much crueller like 200 years ago, people got hung or killed very easily for many reasons (health, accidents, crime, a not very experienced justice system, society view that some people's life os worth more than other's life, ...). When comparing to other stories I've read that happen in a time when there are kings, emperors and a very big difference between "noble" people and poor birth people, personally I don't think the deaths are that non-standard for this kind of story.
About the characters, I actually love when there are a lot of characters, I mean, to me it shows how deeply thought the story is, I hate it when the whole story it's just the main characters and everything is arround them, no side characters, no depth the world these characters live in... So to me, a lot of characters show depth to the story.
About the MC's mother, she clearly hadn't seen him for a long time and she didn't seem that well (either emotionally, mentally or physically), it's just how it seemed to me I guess. And I don't think it's that important as she doesn't appear much, so even that could have been better, I don't think it would have been relevant to the story? I mean he asked her to gather Gula seeds and she didn't even question it, that shows that she either trusts her son that much that even if he acts weird, it's ok, or either she's just that nor well in the head or just someone simple that doesn't question things a lot? Not sure, she is kind of a weird character, maybe we will know more about her in the future?
About what you said that everyone seems dumb but the Mc, I would disagree and agree at the same time. I mean, it's normal that many people aren't very bright as most people there probably don't even know how to right, because in that time normally only the nobles got to study and know stuff so its normal for common born folk to be kind of dumb in certain aspects. But still, we can clearly see that some people are smart in my opinion, but yeah, most of the "smart" people are people that have had extensive studies of various things. Just studying mathematics changes how you think aand view certain things.
About the magic, I have also been thinking that ot isn't very specified, there are no more ingormations ablut what he can do, but that will probably only be told when he goes to the capital? But my conclusion is that his magic can't do things like persuading and controlling people at least, which I think is good, because then he isn't too powerful. And to me it makes sense that he's very smart as he needed to be like that in his "previous life (not sure if it shoyld be called that as we don't even know if he actually died in his time and how he ended up in Ian's body, but it kind of feels like fate, because Ian's body is very similar to his in appearance from what I remember (?))".
I also have a lot of questions, but am having a lot of fun reading this, I hope they make the "fight" between him and the princes very long and political but still using magic!
It was wonderful to read your thoughts about this story, always good to see other views on something I like.

Yo! ( ̄▽ ̄) / thanks for sharing your point of view and it's so good to see your thoughts. The questions are still there although some of your explanations gave me an idea that maybe it wasn't as unreasonable as I believe it to be, especially on the killings part, and we can't forget that the story is still ongoing so we can still see if our questions are still unanswered after some time (๑•ㅂ•)و✧
I still have some reservations about the characters but it may be the problem with the storytelling itself or maybe the limitations of its media (as a manhwa in this instance) since different medias can only tell a story within their own limits (manhwas are limited by the artists' interpretation if it's not originally a manhwa). I won't know unless I've consumed its other media as well (which idk if there is but I'm sticking to the manhwa for this work lol)
We'll see how it goes for now, especially since it is interesting in its own way~ (๑•ㅂ•)و✧
I get that his setup/design is like a genius and politically-astute individual and stuff, but there's a lot of plot holes and I dunno if it's just like that or I missed something
It's still ongoing work but I kept wondering "what is he even fighting for?"
The other characters.... I just can't love them. Like, the maid took a lot of his food before and somehow it makes sense that he's left with just bread? Then she's become a vital part of the mansion? Also, the same maid was seen to have a listening device as well but there was no scene where she reported to the MC? What was that part even?
The MC's mother as well: she didn't even notice that her son changed? Maybe she and the MC were far apart at some points but they act so close as if nothing was wrong. I dunno, she feels... Flat when it comes to characterization. Like, she's the "MC's mother" who is pretty and that was it.
And the amount of people he's been killing, whether directly or indirectly, just doesn't make sense. The characters are introduced, only to off them unless they're somehow wicked enough to be part of a plot. The Assassin, Petrior, feels like he can be more you know? But then he dies. The Brach Soldiers (said to be on par with "Barbarians") were offed just like that. Betty Elise (the girl from the capital), was discarded and feels a bit too characterized as a "bully" who acts on her greed but doesn't have the IQ to match it. In other words: everyone but the MC is dumb.
Don't get me started on his magic: what even is the extent of his power? Like, there's no backlash? No newton's law of conservation or something? It's too convenient that there's not much challenge to him
I have so many questions and so I am both loving and hating this work I hate it for the plotholes but I love it for the art and political battles that somehow may or may not make sense.
I'm still gonna read this lmaooo sorry for the long rant, I had to put it out there somehow