Broadway-bound "To Kill a Mockingbird" faces lawsuit from Harper Lee's estate; Met Opera fires conductor James Levine; "Musicals Tonight!" and The Actors Company Theatre to shudder;  3 new musicals in development: one about Joy Mangano, "Tennessee Whiskey: The Musical", and "Dangerous"; Susan Stroma's "Little Dancer" gets new life in Seattle;  Tony-winner Sammy Williams dead at 69; Ben Platt and Lin-Manuel Miranda collaborate on song mashup for the March for Our Lives Foundation