Thanks, all.
@thumper1 right now, he is living with his older sisters at the family home, with a lot of visits from grandparents and aunts. He turns 18 in two weeks, so whatever legal concerns there might be with this situation are going to be a moot point extremely quickly. The lawyer the family has talked to about the PoA hasn’t, as far as I know, brought this up as an issue.
The helpful link that jonri posted notes that people under a legal guardianship as minors may be considered independent for the purposes of aid. The difficulty here is that if this had happened a year ago, he almost certainly would have wound up under a legal guardianship, but because of the timing, he won’t. I’ m hoping that the college acknowledges the fact that for all intents and purposes, he’s in the same situation as a student who had been placed under a guardian’s care as a minor and chooses to treat him as independent.
I agree this will take an in-person visit. I’m also hoping to get the guidance counselor on-board, although he doesn’t go to a great high school and I’m not sure how helpful she’ll be on this kind of issue.