1. Place the water in a small dish or shallow plate, and sprinkle the gelatin over it as evenly as you can.
2. Scoop the pumpkin puree into a bowl and combine with the spices; set aside, covered, in the refrigerator.
3. Combine 3 cups of milk, the sugars, and the vanilla in a pot and heat on medium, stirring, until steam comes off the top or the temperature reaches 170°F.
4. While the milk is warming up, whisk together the S&C milk and the egg yolks in a large mixing bowl.
5. When the milk reaches the proper temperature, temper the egg mixture with it, whisking all the while. When thoroughly combined, return to the pot and the heat, and cook for an additional 3-5 minutes or until the mixture can coat the back of a spoon.
6. Remove from the heat and transfer back to the mixing bowl, adding in the gelatin. Whisk until the gelatin dissolves, then add in the remaining 3 cups of milk.
7. Place in the refrigerator, covered, to sit for two hours.
8. In a blender, combine the pumpkin and spice mixture with 1 1/2 cups of the custard.
9. When the mixture is uniform, add back to the custard and whisk to combine.
10. Pour the mixture into an ice cream machine and churn for 30 minutes, adding the graham crackers according to your preference.
11. Transfer to an airtight container and freeze for 2 hours.