if your child is not supporting more than 50% of his own support and you are not either, who is supporting the rest?
from everything you wrote I also agree you can claim him. Note: he has to state on HIS return, he CAN be claimed!
Also, it might be best to use this IRS tool, which makes it quite easy to go through any and all permutations.
https://www.irs.gov/help/ita/whom-may-i-claim-as-a-dependent
