Place the octopus, peppercorns, thyme, bay leaf, water, wine, lemon juice, garlic and 2 tablespoons salt in Dutch oven or stockpot. Place a weight such as a plate on the octopus to keep it submerged. Cover and heat to a boil over high heat. Reduce heat to low and simmer, partially covered, for 1 hour or until tender. Test for doneness by piercing the octopus with a knife. Remove octopus, let cool.
Cut tentacles off the body portion of the octopus. Brush tentacles with oil and sprinkle with remaining ½ teaspoon salt and pepper. Grill tentacles over medium-high heat for 6 minutes per side, rotating after 3 minutes to create crosshatch marks. Cut grilled tentacles into 2-inch pieces.
For the salad:
Heat ¾ cup oil and garlic in a saucepan over low heat and cook for 5 minutes; add red pepper flakes and remove from heat. Stir in wine, parsley, lemon juice, 1½ teaspoons salt and black pepper.
Coat tomatoes with 1 tablespoon oil. Grill over medium-high heat for 5 minutes or until slightly charred, turning occasionally. Cool and chop.
Brush bread slices with remaining 3 tablespoons oil. Grill over medium-high heat for 2½ minutes per side or until crisp; sprinkle with remaining 1 teaspoon salt.
lace arugula, octopus, tomatoes and 2 slices grilled bread on salad plate; spoon dressing over salad.