Remove cheese packet from packet of macaroni and cheese and set aside. Bring a large pot of lightly salted water to a boil. Cook both amounts of elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes. Drain. Pour hot pasta into a large bowl.
Stir butter into macaroni until melted; mix in milk and the reserved cheese packet, stirring until thoroughly combined. Mix the processed cheese spread into the hot macaroni and let melt; mix thoroughly. Stir in thousand island dressing, tartar sauce, and vinegar. Cover bowl and refrigerate until cold; salad holds up to 5 days in refrigerator.