1. To prepare fritters, weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and next 5 ingredients (through red pepper) in a large bowl, stirring well with a whisk. Combine buttermilk and eggs, stirring well. Add egg mixture, corn, and crab to flour mixture, stirring gently until moist.
2. Heat a large nonstick skillet over medium-high heat. Add 2 tablespoons oil to pan; swirl to coat. Add 5 (1/4-cup) batter mounds to pan, pressing each with the back of a spatula to slightly flatten. Cook 4 minutes on each side or until golden and thoroughly cooked. Repeat procedure with remaining 2 tablespoons oil and batter.
3. To prepare guacamole, combine tomato and remaining ingredients in a bowl. Mash avocado with fork to desired consistency. Serve with fritters.