I'm also from Ohio, we have a normal amount of sunshine in the summer and winter months
Try 1000-3000 daily and get retested in 6 months. If it's dropped up the dose a bit. Do with your doctor as they need to watch calcium levels too.
5,000iu is closer to a maintenance dose. If you take too low of a dose your D3 levels will drop within a month or two. Even if there is sunshine, the UVB rays needed to convert D3 in your body aren't available in Ohio until Spring.
Very good you're at 64ng/mL now!!
Take magnesium and Vjtamin K2 it will regulate your calcium levels