For the cheesecake: Preheat the oven to 375 degrees F. Cut the pumpkin in half, remove the seeds and place cut-side down on a baking sheet lined with parchment paper. Roast until the pulp is soft, about 1 hour. Let cool and scoop out the pulp.
Using a stand mixer with the paddle attachment, paddle the cream cheese until soft. Add one cup of the pumpkin pulp and mix together thoroughly. Reserve the remaining pumpkin pulp for another use. Drizzle in the condensed milk, then the lemon, vanilla and spices. Transfer to an airtight container and refrigerate for at least 30 minutes.
For the rum raisin eggnog: Combine the milk, cloves, cinnamon and 1/2 teaspoon vanilla in a saucepan and heat over the lowest setting for 5 minutes. Slowly bring the milk mixture to a boil.
In a large bowl, combine the egg yolks and sugar. Whisk together until fluffy. Slowly whisk the hot milk mixture into the eggs. Pour the mixture into the saucepan. Cook over medium heat, stirring constantly, until thick, about 3 minutes. Do not allow the mixture to boil. Strain to remove the cloves, and let cool. Stir in the cream, the remaining 2 teaspoon vanilla, and the nutmeg. Refrigerate for 30 minutes. While the mixture cools, soak the raisins in the rum.
For the graham cracker crumble: Lower the oven to 325 degrees F.
Stir the graham cracker crumbs, brown sugar, cinnamon if using, and salt together in a large bowl. Add the melted butter and stir with a fork. Spread on a rimmed baking sheet and bake until just starting to brown, 10 to 15 minutes. Reserve.
For the huckleberries: Combine the huckleberries and sugar in a small saucepan. Bring to a simmer and cook until thick and syrupy, about 10 minutes. Reserve.
To assemble: Transfer the cheesecake to a piping bag with a large round tip. Transfer the milk mixture to a stand mixer with the whisk attachment and whip to soft peaks. Strain the raisins and then fold them into the whipped mixture.
Pipe the cheesecake onto each plate. Add 3 spoonfuls of the rum raisin eggnog to each plate, and then sprinkle with the graham cracker crumble and drizzle with the huckleberries.