Responses
In the beginning no, because there is no relation between the kid and lee sayoung beside poison, beside J thought the kid is dying since there are no one take care of him while he is gone. He didn't think the kid is alive
He will know soon enough in the upcoming chapters
He really can't connect that a kid he saved/loved that was /drenched/ in poison and the guy with poison powers??
Come on, son, this one is obvious