I don't think you are delusional as I was thinking the same thing. The whole thing doesn't exactly seem right or really match up between chapters, and it does feel more like him forcing this narrative/his mind making up fake memories to justify what he believes happened. I was confused as to how he could be so sure that was his father when for one, the guy on the floor was badly injured, he'd been lying there for quite a while and I'm not sure how recognizable he'd be between the amount of time that passed between chapter 0 to 24, and the fact that the MC has memory problems and isn't a trustworthy narrative. I am even wondering if the MC even truly remembers what his dad even looks like or if his mind is trying to protect him in some way. Also, Guwon probably doesn't know what his father even looks like to even confirm or deny he did kill his father or not. There was a photo of MCs family that Guwon found, but there was a crack in the glass right over MCs father's face. I don't think the guy lying on the floor was his dad and it feels weird for a dad who apparently cares about their child to say that in the first place about making it painless while also sounding like they'd never been there before and if I'm recalling correctly, it sounded like they wanted to loot the house. I'm hoping we'll get more information and backstory next season.
So i went back to ch 0 to see the guy guwon killed. They have the same build and clothes as the current dead body we're seeing here in ch 24. But the thing is before guwon killed him he said, "I'll make this a painless...". So am I delusional to think the guy on the floor isn't even his dad? And everything is just him justifying the fact that guwon's a real phycho? (=・ω・=)