Although Ido Regressed but there's no humbleness in his attitude considering he was the re...

This is just my humble opinion:
It seems like that on the outside right now, but if you read whole novel, then you'll get Ido's POV and just gonna say - it's not pretty at all. Sure, we relate to this uke cause everything now is told from his POV, but They both failed their relationship in the first life. Which one more or less - it doesn't matter. It's a fucked up situation from the start to the end, and blaming just one isn't right.

What's the novels name? Where can I read it?

I agree my opinion could be baised since I haven't read the novel yet. I'm aware of 2-3 Major spoilers. But You know it's unfair , it's unfair for Sejin who knows nothing. And Ido just knows everything. So if he's seeking atonement , he doing it on his own terms and conditions , whichever feasible , whichever feels right.
While it should be the sole MC's decision to punish his wrongdoer, on his own terms. However, he doesn't remember anything
ML comes out at way to calculative. Someone who micro manages & doesn't like it when things go awry or deviate from og path. He's is dominant , acts dominant while MC finds it hard to say 'no' , he simply just ADJUST.
This is Why I said I don't see Atonement from him yet. Maybe future chapters would show more of that. But this is my take upto recent mahnwa chapters.

I hope that manhwa will adapt whole novel, without leaving out other POV and important bits, cause later Sejin will have a backbone unlike in the first life and Ido will be (are) suffering in atonement.

I googled and read MTL ╮(￣▽￣)╭