It is not NVC responsibility to tell you when he turned 16 he needed police certificate. When you got your letter for documents it was described then. You need to get the certificate and upload it otherwise the son will not receive a visa to come.
When on a drug ban you are required to drug test every 3 months for one year. Either the medical center does it or you get it done. You have to prove that you are clean and sober otherwise no visa will be issued and then you will get NOID