Brush 1 tablespoon of the oil on the octopus (reserving the rest), season with salt and pepper, and add to a pot with enough water to cover. Simmer until the octopus is cooked through, about 20 minutes.
Remove octopus to a utility plate to drain and set aside until cool enough to handle. Remove the octopus head and legs, split in half, then slice and dice small.
Add the saffron to 1/2 cup warm water and let it sit for 10 minutes to allow it to "bloom."
Heat the remaining grapeseed oil over medium high heat in a 16 inch paella pan. Brown the chorizo on all sides and remove to a utility platter. Brown the chicken pieces and remove to the same platter.
Add the onion to the pan and saute until translucent, then add the garlic and gently cook until softened, monitoring to make sure it doesn't burn. Add the white wine and allow most of it to evaporate. Stir in the paprika, parsley, cup of bloomed saffron, and chicken stock, and bring to a gentle boil. Return the chorizo and chicken to the pan, and add the octopus. Stir in the rice, salt and pepper and reduce heat to medium. Cook uncovered without stirring for about 20 minutes, then add the mussels and cover. Let cook until the mussels open, about 7 minutes, then remove them to a utility platter. Add the shrimp to the pot, cover, and cook until they turn pink and opaque, about 5 minutes, then remove the shrimp to a utility platter.
Serve in the pan and sprinkle with fresh cilantro. Arrange the shrimp and mussels on top.