Welcome, ericeric!
It sounds like you and your son have a pretty good relationship, and that just the financial cost of his habit may be enough to convince him to quit. I am not familiar with spice with withdrawal, but I hear most often the suggestion to quit for a year (that may seem like a really long time to a young person...)
You may want to particiapate in some of the discussions here:
Friends and Family of Substance Abusers - SoberRecovery : Alcoholism Drug Addiction Help and Information
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