Be VERY careful with science coursework that way-- some universities (and thinking UC system in particular, but they aren't isolated) REQUIRE that a lab course have been completed in a brick and mortar setting for the course to "count" as a prerequisite/requirement.
My advice on AP exams and physics is too dated to be useful- DD took AP Physics B when it was a one-year course (the course that uni's didn't know what to do with since it has no functional college equivalent, basically).
Let me also offer my sympathies for your family's situation and need to make some difficult choices. I know that it doesn't always seem like it at the time-- but things will be okay in the end. It will be fine-- it just won't be right now.
Have you considered asking a local college application coach?
I have to agree with bluemagic that much depends upon what his range of plans might include-- understanding that the upper end may seem out of reach at the moment if you're all feeling overwhelmed. If you could share what you'd all LIKE-- even if you think it probably is now off the table, that could help us to give you some additional insights into at least not closing the door completely.
