His heart tells him he is a boy in need of maternal approval. Gently encourage when you can, ask him about his dreams and aspirations. The key is to get him to have a hope for his future.
Theresa, This thread includes incredibly good advice. You are in the mother role for this young man and you're essentially reparenting him, even if he is temporarily out of your home. (I believe that he will be back.) Continue to encourage him to complete the tribal paperwork. He mentioned an uncle who has guided him. Help him to explore reconnecting with that uncle. A combination of agencies and professionals helping him (esp. a therapist familiar with trauma, substance abuse and Native American issues); at least partially functioning family of origin members helping him (his uncle?); and friends helping him (you and your family) may help this young man eventually build a functional life. He is very likely to benefit a great deal from learning more abt his tribe and its history, so he can gain some self esteem and an internal sense of self. If there is some sort of tribal male figure (coach? spiritual leader? teacher of some sort?) who can be uncovered to help him, even at least occasionally, that would be ideal.
God be with you and this young man. He certainly has a difficult road ahead of him.