Given your plea for help, and assuming you have already told him to get out - you will have to involve the police. You'll have to report having told him to leave and his refusal, suspicion of drug activity and use, your fear for your family's safety, him using your home to run a business and whatever else you haven't written here. You may also have to go to court to process a "formal" eviction if deemed necessary by law enforcement. If push comes to shove and he will not leave on his own accord, or if he does - but you still feel unsafe - you might consider getting a restraining order. Of course the situation now and likely into the future will make for poor family reunions, but you gotta do, what you gotta do! If not for yourself, for your children!
Best of luck. I'm hoping for a quick resolve to your dIlemna.