Preheat the oven to 350 degrees F (175 degrees C). Spray 2 loaf pans and 12 cups of a muffin tin with cooking spray. Combine pumpkin puree, maple sugar, coconut oil, eggs, milk, and vanilla extract in a large bowl. Combine whole wheat flour, pumpkin pie spice, baking soda, sea salt, and cinnamon in a large bowl. Slowly add flour mixture to pumpkin mixture while blending with a hand mixer to create a dense but moist batter. Add another 1 to 2 ounces milk to moisten batter to a smooth consistency, if necessary. Portion batter among the prepared pans. Bake in the preheated oven immediately until a toothpick inserted into the center of a muffin comes out clean, 35 to 40 minutes. Remove muffins and reposition loaf pans; continue baking loaves until a toothpick inserted in the center of a loaf comes out clean, about 10 minutes more. Remove from the oven and let muffins and loaves cool on wire racks.