
I have read the whole novel and people who consider this a love story (even if the author herself thinks this), are completely delusional.
Leila will not go to college and decide to become a town teacher to Matthias' delight because this means they're together in Arvis. Matthias makes sponsorships to various things including the Leila's school so he has an excuse to encounter her. He "torments" Leila by keeping this gentleman facade to others when he visits the school but makes advances towards her and when she refuses, he pours ink on her.
Uncle Bill will make a massive mistake with an explosion on the mansion garden (something to do with the new electrical work which he was being stubborn about) completely annihilating the precious plants. He was meant to go to prison so Matthias makes this a blackmail to Leila. He will not send Uncle Bill to prison and continue to hire him as long as he can restore the garden... if Leila becomes his whore/mistress.
Leila desperately agrees and Matthias takes her immediately on the floor. Once he's finished, he leaves Leila on the cold floor. This rapey sessions continue with Leila sometimes fighting back because the engagement with Claudine (and Claudine seems to have caught on their physical relationship), is making her guilty as a mistress. Matthias traps her again by blackmailing that he will tell Uncle Bill how Leila has whored herself to him if she decides to end things.
When Kyle gets back for a vacation, he catches Matthias raping Leila again in the cottage, but to save face, Leila tells "I love you" to Matthias to convince Kyle she's in love with Matthias so that he thinks she's not a whore. Kyle does not believe this and gets angry with Leila anyway.
To cut many scenes short, the mistress thing will get spread over Arvis and inevitably reach Uncle Bill. He quickly understands how Leila sold herself for his sake and blames himself. So, he decides to run away with Leila to the other country. By now, Leila has gotten pregnant but they do not address this. Matthias tries to get her back but Claudine,his mother and grandmother prevent him.
Leila and Uncle Bill lives for a short while in this new country but war begins (between the country they escaped to and Matthias' country). Matthias holds a high position in the military and has discovered that Leila and Uncle Bill has been in this country so he secretly was on a mission to track them down while participating in the war. Long story short, bombing by Matthias' country to where they was, killed Uncle Bill and Leila finally calls him "father" on his death bed. Because of the chaos, and feeling lost already Leila decides to go to the sea and die. Matthias finds her with her swollen belly and kidnaps her into the military base. He "nurses" Leila back into health but when she refuses, he blackmails her again that he would kill Kyle(who is also enlisted) in this war. When Matthias realizes Kyle was the only card left, he forces Kyle to be the one to take care of Leila because he knows she won't resist Kyle.
When the war was in a dire moment, Matthias was suddenly urgently needed and he had to part ways with Leila. Leila magically realizes she is "in love" with Matthias and asks him to return to her. (the war was ending with Matthias' country was already winning so i dont get this arc)
Leila returns to Arvis quietly and gives birth to a son, Felix who is the spitting image of Matthias. She prays for Matthias return oh so romantically in the newspaper hoping he's not on the death list. So basically, Matthias fakes his death for a while which sends the Duchy into disarray. This devastation for his mother and grandmother about his "death" was him setting up a "less bad" devastation that he is going to marry Leila, a commoner.
So he marries Leila and Leila can go to college now.
Leila is loveydovey with Matthias as if she wasnt just trapped into wanting to have a family with him now that she lost Uncle Bill. And they have another child who is blond.
(Reading the side stories with Leila and Matthias' marriage is so disconnected with the messed up dynamic they first had and the problems they didn't even resolve)

I read the novel too but I don't recall some of the things you've said. I did some digging and apparently there are some misleading fan translations going around to spark controversy and that Yonder (the website I used to read this on and has the official translation) is the genuine one. Here's the reddit post: https://www.reddit.com/r/MaleYandere/s/iNpJejqmHn.
But still, I do not condone what Matthias did to Leyla is any way. He still treated her like shit and SAd her.

Sorry, wrong link lol: https://www.reddit.com/r/MaleYandere/s/m9hlGozFui

there are untranslated chapters until ch57.....
-ch51 is incomplete here. It actually shows ML bringing baby to MC to kiss his cheek. then at night, while ML is sleeping beside him, MC finally wakes up
-the doctor and excrown prince is having sex and they briefly show a backstory of how they met in childhood
-the older brother of ML and the balckhair person is playing with the baby and it seems that he is pursuing the ML's brother. they finally allow the excrown prince to see the baby
-i think MC was having serious postpartum depression and grief from having their kingdom destroyed so he was being closed off towards the ML
-last ch57 so far, we end with MC finally visiting his baby
I WANNA HUG THAT WAIST TOO!
( ̄へ ̄)