Been there. Draw some hard lines, never back down. Be open and ready to help but by your standards, the ones he grew up with. Since he chooses the hard life then he has to be free enough to finally lick the bottom of the systems boot. Eventually all his lying, thieving friends and cheating women will let him down and he'll figure it out. Probably while sitting in a jail cell.
Learn how to use your city and county online jail intake records, how to deposit a few bucks for phone calls, emails and how to visit. They listen real good when wearing a striped suit. The third time seems to really wake a fellow up. Mug shots and arrest records showing up when he google's his name usually has an impact too. Have a scrap book I made for him. He hates it. Yeah the nightmare is over - finally.