Yeah i agree, i would even be fine with the MC being somewhat shitty (at least in the past) and recognizing it and owning up to it. But i feel like his thoughts are too judgemental towards Zeke and his talks with Keyla to if thats the case.
The MC just feels like such a hypcrite to me in this situation, how can he seriously judge or reprimand Zeke for anything while he fucked his girlfriend and future wife behind his back for months.
Honestly, I'm surprised they still got along after that. The MC has been best friends with Zeke going on 6 years. He didn't know Zeke had been cheating on Keyla as well (so this wasn't a factor), yet he had no shame and still remained best friends despite betraying him that way. The same MC who's constantly spouting pop-philosophy and faux-psychology about life... He decided that it's better for Zeke to live in ignorance, instead for him to come clean.
It takes someone who's very cold and calculating to do that. It would've made more sense for their friendship to fizzle out, due to guilt.
And all this stuff about Zeke doing it out of desperation and gaslighting keyla into agreeing was just dumb and even Keyla herself explained (in her confused way) why she did it. She said yes in hopes to move on and to not intervere with mc/kim not because Zeke forced her into it lol. This gave me the worst white-knight implications, Zeke is to blame because he is the guy (and not the mc himself).
Agreed. What was Zeke desperate for, if he was fucking anything that moved? And Keyla's reasoning for agreeing to marry him made no sense to me. She continued seeing Zeke, MC got together with Kim, and eventually Keyla decided she wanted to come clean. Then Zeke proposed and she said yes... Like you say, her motivation was about not ruining things between MC & Kim. But, I can't follow that logic. This would only be true if Keyla thought that MC would break up with Kim for her, or if she didn't trust herself for not trying to ruin their relationship.
I even kinda like Keyla and Zeke in this situation more than the mc at the moment. Keyla and Zeke just seemed to be very very confused and dumb and not able to made sound decisions back than, while the MC feels more like a backstabbing snake or a coward even more as he is very adamant about keepin everything a secret forever.
And it doesnt really fit with the mc's character in the other parts of the avn, we dont see him behave like that usually, i would even say its contrary to his character behavior.
For me, personally, Keyla is
most wrong. The MC wasn't seeing anyone at the time. While he did betray "his bestest friend ever", Zeke, Leyla should've been the responsible one. It was her choice to remain in that relationship while cheating on him.
From the lens we're looking through, I do think you're right that it paints the MC in the worst way possible. He's usually so logical (sometimes bordering robotic), and an endless fountain of platitudes... Yet we don't see him really living up to it himself. If it fits his character, I think that depends on the choices you make. It's possible for the MC to date multiple women at once, which the game more or less seems to consider cheating. For instance, Aurora will turn down a date if Lydia saw the MC at the art gallery and said he's her boyfriend. Even if all the MC did with Lydia was kiss, they're considered a couple by the game's logic.
Don't you just want to snowball fight her? 
