"...if progress is being made and he's not yelling at people and being unpleasant."
You have answered your own question regarding how to proceed, Origami. If he were two, you would set parameters around his behaviors and your responses to them.
You are correct in your thinking that this nineteen year old still requires teaching and parenting and stability. Everything will change once the Court date has come and gone.
Is your son applying for work, or thinking about school? Could boredom and feeling like a loser be contributing to his behaviors? Would it help if he were to volunteer at an Animal Shelter, do you think? This would provide structure for him, and so many living creatures to care for and about.
That might help him very much.
Cedar
