The first thing that comes to mind is putting an alarm on the house so that every time an exit door is opened the alarm chirps. Also, set the alarm at night and only you and your husband will know the code to disarm it for a while so that your son can not sneak out of the house at night without the alarm setting off.
Another option would have him to talk to a counselor about peer pressure and making decisions. He needs some sense of direction and a neutral party may be able to offer that.
Please take some type of action before negative consequences occur. You have been very lucky so far.
Please ACCEPT so that I may be paid for my efforts!!!! Thank you. Have a great day!!!