Stir together mayonnaise and garlic; cover and chill until ready to serve.
Whisk together olive oil and next 4 ingredients for a vinaigrette; add tomatoes, and toss well.
Combine flour and next 3 ingredients. Dip crabs into egg, and dredge in flour mixture. Sauté crabs in hot vegetable oil in a large skillet 2 to 3 minutes on each side or until golden. Drain on paper towels.
Spread 1 tablespoon mayonnaise mixture on each toasted bread slice; top with crab and 1/4 cup tomato vinaigrette. Dollop with extra mayonnaise mixture, if desired, and top with micro greens or sprouts.