I think from all the theories of other people I've read about the "Fate" in store for Kim Dokja that He loved the TSWA/WOS so much that the mother realized at some point before the fight with Lsk's faction and Yjh's faction began, the flashback to them in prison where Kim Dokja said to her mother that he "didn't want it to end." I think that "the one he loves the most that will kill him" is TSWA itself.
Also now that I remember it while typing is that we don't fully know what the "Fourth Wall" is capable of other than protect kdj from any mind anomalies/attacks/breakdowns except when he confronts with his mother from chapters 194 - 200s. I think I remember something along the lines of "The fourth wall is greedily smiling..." ( ... because I forgot what the full sentence was.)
P.S. - This is, so far, my "own opinion" from what my little brain can process atm, and others are free to correct me or add their theory on top of mine. Also, the mother and son relationship to me is so sad, even further beyond sad. It's so strained that it's impossible to mend it back together.