It's obvious that you care very much for Isaiah, and you are to be commended for that!
Have you considered trying to become his foster parent(s)? Of course, I don't suggest this lightly. This is something that your whole family needs to be on board with the idea. The one advantage to fostering him would be that you would get a monthly stipend for his care plus local social services would provide counseling, tutoring, etc. Also, Isaiah would have to be a willing participant to this. Fostering him would give you the advantage of being able to "lay down the law" regarding family rules and what would be expected of him once he is part of the family.
If this is something you want to do, the first step would be calling Child Protective Services and letting them know you would be willing to foster him. Of course, this is a long and involved process with lots of red tape---not easy to have to get through.
I wonder---has the school been in touch with CPS at all? The law says that if the school knows about a child with a bad home life, the school must report this to CPS.
Again, this is a lot to consider. I truly admire people who have the time, energy, commitment and love to foster children. All that said, you're right --- your child's well-being is your first priority. If you decide you don't want to foster Isaiah, you shouldn't feel bad about that.
Good luck with whatever you decide to do and bless you for caring so much about this child. Whatever happens, someday he will look back and realize how fortunate he was to have had you all in his life.