It must be so frightening for you to watch your son exchange one addiction for another. Let's first equip you with some information about methamphetamines (meth) and where to start to get help for you and hopefully for your son. Googling meth psychosis results in many different sites offering great information. I found this one from The Recovery Village to be very extensive with its information
– Meth Psychosis: How Can Meth Use Cause Psychosis and Hallucinations https://www.therecoveryvillage.com/meth-addiction/meth-psychosis/#gref
I hope other members, like @hisgrace6992 and @msmelissalc, can direct you to their preferred online resources and possible first-hand experiences with meth psychosis.