1. In a bowl, whisk together garlic, ginger, scallions, crushed red pepper, rice vinegar, 1/3 cup pineapple juice (from can), sugar, cornstarch and 1/4 cup water.
2. Sprinkle pork with salt. Warm a large skillet over medium-high heat. Pour in vegetable oil, and when very hot add pork and stir-fry until no longer pink, 3 to 4 minutes. Add bell pepper, snow peas and water chestnuts; sauté for 3 minutes. Stir in pineapple.
3. Add reserved sauce to skillet and cook, stirring, until thickened, about 3 minutes. Divide rice among 4 plates and spoon pork mixture on top. Sprinkle with peanuts and scallion greens and serve immediately.