Combine salt, mustard, thyme and pepper; mix well. Rub salmon fillets with honey and sprinkle with seasoning mixutre; reserve remaining seasoning mixture. Heat 2 teaspoons olive oil in nonstick skillet. Brown both sides of salmon fillets. Toss spinach and garlic with remaining 1 teaspoon oil in 13x9x2-inch baking dish. Place salmon on spinach, cover loosely with aluminum foil and bake at 300 F for 10 minutes. Sauté grapes in skillet used to brown salmon. Add wine, bring to boil, season to taste with remaining seasoning mixture and salt; reduce by half. Serve salmon on spinach; top with grape sauce.