I think that maybe the "I SEE EVERYTHING" line was more about what he saw after he left the world. That he saw everything clearly now because he was no longer suffering.
The narrator contrasts and says that his eyes are closed and that he'll never forget the steadfast faith of the boy and his mother, so maybe he is saying that though he's never felt anything close to what this boy and his family has felt, one day his eyes may be opened as well.
I think that maybe the "I SEE EVERYTHING" line was more about what he saw after he left the world. That he saw everything clearly now because he was no longer suffering. The narrator contrasts and says that his eyes are closed and that he'll never forget the steadfast faith of the boy and his mother, so maybe he is saying that though he's never felt anything close to what this boy and his family has felt, one day his eyes may be opened as well.