First, that channel is pretty dead. No new videos for over 5 months.
Second, I think kingwalt360 was meaning you post a comment to his latest video (which is, again, five MONTHS old). If the channel is dead (or in a deep coma), he's not visiting its dashboard and thus probably not getting any notification that anyone has posted anything to his community page.
Third, he also has soundcloud and instagram pages. Links given on his "About" page. Both of which also appear to have been dead for the last five months.
Fourth, try DMing him on Instagram as he tells you to there.
Fifth, do realize that you're trying to get in contact with a 16 year old. Five months to a teenager is 10 years to an adult.
He probably has forgotten that he even has a YouTube channel.
Good luck!