In a large bowl, combine the flour and salt and pepper, to taste. Add the rabbit, coating it well with the seasoned flour. Heat a large saucepan over medium-high heat and add 4 tablespoons of butter. Remove the rabbit from flour, tapping off the excess and add to preheated pan. Saute the rabbit until browned. After browning, pour in 2 cups of port and deglaze the pan. Remove rabbit to a plate and set aside. Add the stock, remaining butter, thyme, garlic, bay leaves, onion, carrots, celery, sweet potatoes, and rosemary. Reduce the heat to medium, cover and simmer for 30 to 40 minutes, stirring occasionally. Deglaze with remaining 1 cup of port, and then add tomatoes. Return the cooked rabbit to the pan along with a generous pinch of nutmeg. Simmer until the desired stew thickness is reached, about 10 to 15 minutes. Season with salt and pepper, to taste. Transfer to a serving bowl and serve.