And all this certainty when all we know is he earns a lot more and you sold the house.
Not how much profit or where the kiddo has in mind for college. Big difference, applying to a FAFSA-only that can offer a lower price point, aid, merit, or state funding, and that won’t look at Dad’s picture. We don’t even know what kiddo may qualify for.
100k profit that would be eaten up at 35k/year college costs? (Assumes he pays half.) Or 400k and a reasonable expectation OP set aside $x? What $x?
Get a lawyer or consult but the chances they understand fin aid, financing, merit aid, or college options, is slim. OP still needs that understanding.