In a large saute pan over medium-high heat, add lemon juice, white wine, and the mussels. Cook until the liquid dissolves. Reduce the heat to low, add balsamic dressing, parsley, thyme, and tomatoes. Continue to cook on low heat for 3 to 4 minutes, stirring to prevent the dressing from separating. Remove the pan from the heat, and allow the mussel mixture to cool. Add the mussels and sauce, the spinach, feta, and the corn to a large serving bowl. Season with salt and pepper, to taste, toss and serve.