Responses
I'm thinking it's ptsd + dissociative amnesia, cause his memory loss is mostly when he feels like he's in danger and with traumatic events, and not the usual things that patients with dementia forget first. it could also explain suddenly attacking guwon with the knife.
It's a high chance of trauma in a way since he remembers bits and pieces of his life before the attack or apocalypse
During jinwoo's dizziness it may be an hallucination since he had already had a dream about this and gunwon not being able to lie, he already said he hasn't killed his father which that topic is out the question
Jinwoo already has amnesia or some form of dementia.. so he'll probably go crazy in the progressing chapters (*just a guess*)