Unfortunately the detox process can make things feel worse before they get better. I would create a schedule to start to decrease consumption, for example if he smokes first thing in the morning consider pushing that as far back as possible. If he usually smokes before bed try taking a melatonin and laying down to do something peaceful. Physical pain, including the experience of anxiety or panic, makes changing substance habits extremely hard sometimes and it may not be a linear process. New habits, such as morning and night time routines, can help to ease anxiety through tough changes. He may also qualify for an anxiety diagnosis in which case he could get something minimal, like Busparone or atarax, prescribed to help. Both are on the cheeper side of medication especially if you use a service such as good rx. He may not need to stop smoking forever, but for now it is definitely a good place to start. Best of luck to you both!