Combine shrimp, 2 tablespoons vinegar, and chili garlic sauce in a large bowl; toss well. Cover and chill 1 hour.

Combine remaining 3 tablespoons vinegar, oil, and next 6 ingredients (through salt) in a small bowl, stirring with a whisk.

Place 2 cups spinach on each of 4 plates; top each serving with 1 cup shrimp mixture. Arrange 1/4 cup mango, 1/4 cup radishes, and 1 tablespoon avocado around shrimp on each plate. Top each serving with 2 tablespoons green onions and 1 1/2 teaspoons pumpkinseed kernels. Drizzle each salad with 2 tablespoons vinaigrette.