Combine 2 tablespoons salt, brown sugar, garlic powder, paprika, onion powder, oregano, and black pepper in a small bowl and mix well.
Place pork pieces into a large bowl. Rub spice mixture evenly over the pork, pressing until it adheres. Add in onion, garlic, cinnamon stick, and bay leaves.
Squeeze orange juice into the bowl with the pork and toss in the juiced orange pieces as well; toss to combine.
Place pork mixture into a sous vide-safe vacuum sealer bag. Seal bag and immerse in a heat-proof container of water with a sous vide cooker. Set temperature to 165 degrees F (74 degrees C) and add the ping pong balls on top. Cook, occasionally re-adding water as it evaporates, 12 to 24 hours.
Remove pork carefully from the water bath and transfer contents into a large bowl. Pick out the chunks of meat with tongs and transfer to a rimmed baking sheet. Discard everything else left in the bowl. Let pork cool briefly. Shred using 2 forks or your fingers and spread evenly over the baking sheet. Season with salt.
Set oven rack about 6 inches from the heat source and preheat the oven's broiler. Place pork under the broiler and cook, flipping halfway through, until fork-tender, about 10 minutes. Watch carefully so it doesn't burn.
Place tomatoes and green chiles in a food processor and blend until pureed. Pour into a saucepan; add chicken stock, rice, butter, chili powder, cumin, oregano, 1/2 teaspoon salt, garlic powder, and onion powder. Bring to a boil. Cover and reduce heat to low. Simmer until Spanish rice is tender, about 25 minutes.