Use the qualifying child support worksheet on page 16 of Pub 501 to determine whether the student provided over half their support. As MiddKidd86 posted, do not include amounts from scholarships/grants when going through the worksheet.
Generally, scholarships/grants received for finaid aren’t held against students for future finaid. FAFSA has questions that will subtract out finaid in the EFC formula. Generally, colleges will do the same in determining future finaid. Filing status shouldn’t matter either, though if you are paying for medical insurance for the student, providing food and shelter during summers and breaks etc., you are likely to still be able to claim your student as a dependent per the worksheet. Being away at school is considered a temporary absence for education.