You can comfortably see Ohio in an afternoon as you drive through it at 55MPH - no need to stop. Unless you want to go to Cedar Point that is. 2 days is more than enough at the amusement park.

Maine is worth a visit. New York City is worth multiple visits. Same with Boston. DC 1 to 2 days tops unless you are going to stay inside museums all day, in which case you may need additional days.