You can't force an adult to get help.
Since he is 19 years old now, and receives such a large lump sum of money every 6 months, is there any reason he shouldn't be living on his own?
When my oldest daughter got pregnant, and decided that school was no longer important, that she'd rather play house with the baby's daddy, her father and I signed the emancipation papers. She was 17 years old. He also made it clear that there would be no more child support for her care since she wanted to be an adult.
With the exception of one month that I took her in against my better judgment, she has never lived at home again.