How do we deal with the whole chaos?

Let him go. Trust me, he really needs this now in his life. When you're a parent there's alot of things you worry about happening to your children/step children but this young man needs this right now in life. You're other two sons might think that you're treating them differently but hey, you are treating them diferrently. All kids needs to be treated differently ( in the CORRECT way ). All kids are different.