
"Is he even single?"
No girls, he's wishy-washy in all but his job. He's a potential train reck and one of you found out the hard way and is still hanging into the caboose.
Get over him because he's the primary fuel for your continued beef with your old bff, we haven't even see you with your kid (or only once because I don't remember how we found out you do have a kid) much less him, and if he hasn't put a ring on it, he ain't ever.
It would solve this arc with one chapter, though an apology/coffee therapy session with Jiah would be nice.

The second I heard five years, no fighting, my thought was "She gave up putting up with him." Just like the guy said she didn't remember he didn't like pork, he likely did much of the same before then. My mom has gotten very tired about all the little things my dad doesn't notice, both that she does and he doesn't notice he does.
As for the anniversary thing, it depends on how the person is with dates in general. My dad and I are great with remembering birthdays and the like while every so often when my mom fills out a form, she has to ask the day of the month I am born on.
Our couple doesn't have that problem. I wouldn't say they are fighting every day so much as they are communicating.

I used to try to remember as much as I could about my bsf and be as receptive as I could to everything she wanted to talk about. But she starting ignoring me when I wanted to talk so I did it back and she probably thinks it was equal or just me but I just couldn’t handle it anymore (we don’t talk anymore)

Everyone is a bit slimy. Kanna is straight up mental and the crown prince is giving off yandere vibes but everyone has that layer of human grime. It's both leaves a bit of an icky feeling reading the characters' thoughts but also fascinating because they feel more real than the near Mary Sues prevalent throughout this genre.
...I'll keep reading to puzzle out my feelings on it.

Okay, yes, I am staying for the story.
But can I gush for a few sentences about how they are using proper etiquette when taking their tea? Except when they studied in the library. So many comics set in this time period only pick up the cup and leave the saucer on the table and it's like getting water in your shoe to me. I'll even overlook that they don't show both hands putting down the two since I know it would look awkward on a still frame.
Just great job, author. Fine attention to detail. Please keep going.

Father Evan has half his mind back and is putting his foot down. Sir, your daughter is the same strong, intelligent woman your wife was. You know she'll make the best choice for her self. Let your new son-in-law over the entire kingdom to prove his love like he's already planning to do and let it happen.

"Wow, you're so skinny!"
Except her boobs are each bigger than her head. I understand it is a comment about how she has been deprived of food but there are women who have body proportions to where they would be underweight and still have curves, just not that large. And those villainess dresses must be made of magic to not only stay on but also keep her ladies lofted. I've friends as large and they don't like working out because they have to wear 2-3 sports bras so they don't get hit in the face. Those dresses would be a nightmare for them.
Though Jenia seems like a parroting type of kid, little kids say off the wall things all the time. Misinterpreting is part of their language learning process. Or you have behavioral copying, like the child who got into a stranger's car because he thought it was an Uber; he only ever saw the car pull up and didn't understand the difference.
What I'm saying is, our BunBun may not have said such a thing but she's running as a general rule.