I have seen/heard too many tales in the
drug-riddled area I live in where people will comply with CPS orders for
drug rehab but the second CPS is gone (in your case, it'd be he knows he has your complete trust back) and they aren't being held accountable, they sink right back to it. Rinse, repeat.
It may be that he is genuine, but there has been A LOT of damage done to your relationship by the cheating and the dishonesty related to drug use.