For the ceviche: Add 8 cups water to a small stockpot with half of the lime juice and 1 tablespoon salt. Bring to a boil and add the shrimp, then cover with a lid and turn off the heat. Poach the shrimp until just cooked through, about 2 minutes. Drain and cool slightly. Cut each shrimp in half lengthwise.
In a large mixing bowl, add the remaining lime juice, the tomatoes, cilantro, oil, agave, tomatillos, garlic, shallots and 1 teaspoon salt, and stir together. Fold in the shrimp, then cover with plastic wrap and refrigerate for up to 2 hours.
For the chips: Set two racks in the middle of the oven and preheat the oven to 375 degrees F. Place the lime zest on a microwave-safe plate and microwave on high heat in 1-minute intervals until completely dried out, stopping to stir after each interval. Reserve for a later use.
Stack the tortillas and cut into sixths, then divide the pieces between two large baking sheets and spray evenly with the cooking spray. Bake until crispy, about 15 minutes.
Meanwhile, place the dried lime zest, garlic powder, paprika and salt in a spice grinder and blend to a fine powder.
Spray the chips once more with the cooking spray then sprinkle all over with the spice powder.
For the beans and chorizo: Put the black beans and bay leaf in a medium saucepan, and fill with cold water to cover by 1 inch. Bring to a boil over medium-high heat, then reduce the heat to a simmer and cook, partially covered, until the beans are tender, 30 to 40 minutes. Drain the beans and discard the bay leaf.
Meanwhile, heat the olive oil in a large saute pan set over medium-high heat and add the chorizo. Cook until just cooked through, about 5 minutes. Use a slotted spoon to transfer the chorizo to a bowl. To the pan, add the onions, red bell peppers, yellow bell peppers and 1 teaspoon salt, and cook until lightly browned, 6 to 8 minutes. Add the garlic and cook until soft, about 2 minutes. Stir in the cumin, ancho powder and chipotle powder, and cook until the spices are lightly toasted, about 2 minutes. Stir in the chorizo, beans and stock. Bring to a boil, then reduce to a simmer. Cook until the stock reduces by half and the mixture thickens, 6 to 8 minutes. Season with more salt if needed.
For the cheese sauce: Heat the oil in a large saucepan set over medium heat. Add the garlic and onions, and saute until tender, 5 to 7 minutes. Stir in the stock, cauliflower, squash and 1 teaspoon salt. Bring to a boil, then reduce the heat to a simmer and cook, covered and stirring occasionally, until the vegetables are tender, about 20 minutes.
Transfer the mixture to a blender and carefully blend until completely smooth. Return the sauce to the pan set over low heat and add the Cheddar, Parmesan and chiles. Stir until the cheese melts. Taste and add more salt if needed.
For the chile and cilantro sauce: Preheat a grill pan to medium-high heat. Grill the garlic, Anaheim chiles and poblanos on all sides until deeply charred, about 15 minutes. Remove the skins from the garlic, and set aside. Place the peppers in a bowl and cover with plastic wrap. Steam the peppers for at least 5 minutes, then peel the skin away from the flesh. Halve the peppers and remove the seeds.
In the pitcher of a blender, add the peppers, garlic, cilantro, sour cream, yogurt, scallions, agave, salt, lime juice and lime zest. Blend until smooth.
For the nachos: Divide the chips among 8 small plates or bowls, and then top with 1/4 cup of the black bean and chorizo mixture, 1/4 cup of the cheese sauce, 1/3 cup of the shrimp ceviche and a drizzle of the creamy chile and cilantro sauce (about 1 tablespoon). Top each with 1 tablespoon of the queso fresco and a sprinkle of the cilantro leaves to serve.
When blending hot liquid, first let it cool for five minutes or so, then transfer it to a blender, filling only halfway. Put the lid on, leaving one corner open. Cover the lid with a kitchen towel to catch splatters, and pulse until smooth.