He may not only be a dealer, but he may be selling other items hot or stealing items from stores or other people. His fake credit cards could land him in big time trouble.
You have no choice now. Time to get all this stuff together, sit him down, and confront him with it, demanding he get help and cutting off all of his "toys" that allow him to sell this stuff. That includes the car. He shouldn't have access to it. Do you think he could be stealing from work? I knew a kid who did that and, whoa, did he get into trouble once he was caught. He stole items and money from the cash register and he was only sixteen or seventeen, but he ended up in a residential treatment center.
Your son is not who you think he is. Don't feel too bad. None of our kids were who we thought they were. Drug users are very deceptive and quite good at playing the game. At this point, if it were me, I'd call the cops so that he could face the consequences as well as get the help he needs before he turns eighteen, when you will not have much control. If you don't confront him and force him to face hard consequences, he could end up in jail soon without your being able to do anything.
This is beyond what my daughter did. She never had a lot of money on her. Your son is dabbling in things with dangerous people who could threaten or take his life. You MUST turn him in to protect him. Don't make excuses for going through his room. Do not let him guilt you. This is on him.
You may want to check his cell plhone messages and Facebook to get an even clearer picture. The more you know, as hard as it is to learn, the more you can help him. H emay be in danger because of whom he is associating with and YOU may be too. Change those locks! If possible, get an alarm on your house. Your son is playing with fire.
I would certainly not be planning for him to go away to college next year. I would worry about getting him help NOW and worrying about his education later.
I am soooooooooooooo sorry about this, but it is honestly better for him and even for you to know. I highly recommend going to a Nar-Anon meeting so you can get real time support from parents who know what you are going through.
Keep posting as we understand. You will find that most people really DON'T get it. People at Nar-Anon meetings do get it. This just isn't something you can confide to just anyone.