Sooo I am speculating that Mincheol first tried to earn more for the two of them and made ...

Sooo I am speculating that Mincheol first tried to earn more for the two of them and made efforts to try making things better, because he genuinely loved her and wanted to do it for their future. However, as the results never really came out as expected (or as he may have desired), resentment may have built up overtime from thoughts of "If only I had done THAT back then... If only I had not done THIS..." etc.

Very much real, I have seen things like this happen irl. People who are oh so in love with each other may blame their relationship when things get awry in life. You don't want to blame yourself for your decisions because it's scary. Scarier and tougher than blaming someone else, who may have been the reason behind many of your bad decisions in the past, even though they never actively told you to do any of it.

So what do you do? You blame it on the other person, feel 'free' of the weight of all of your poor decisions but it's just an illusion at the end of the day. You know it just as well as anybody else that whatever happened was because of YOU.

I do not like Mincheol, but I do not hate him either if I am being honest. I have had this happen between me and my sister, although nowhere as severe as this shit ofc. Things are better now because I took the time to get my mental health together and get my life fixed, which eventually made me realize how I had been attributing my misfortune to someone who wasn't really actively involved in any of my actions. There is no saving Mincheol and Haesoo's relationship though and that's for the better ig.

And I do think all of these chapters showing the past and what's going on in Mincheol's head are indeed an important part of the story. A story is built from all of it's characters, whether you like them or not.