Combine vinegar with salt, honey and mustard in a small bowl. Whisk olive and vegetable oil gradually until blended. Correct seasoning.
Place lettuce in a bowl and toss with half of the vinaigrette. Divide in 2 plates.
Combine crab meat with parsley, chive and 2 tablespoons of remaining vinaigrette. Season with salt and pepper. Arrange crab mixture on lettuce. Garnish with grapefruit segments and avocado slices.
Drizzle over with remaining vinaigrette.