“How To Dance In Ohio,” the new musical that opened Sunday night at the Belasco Theatre, marks a laudable first for Broadway: A show about autistic persons who are actually played by actors with autism. But as groundbreaking “How To Dance” is as an idea, its execution across the board does not match its admirable intentions. The show, directed by Sammi Cannold, waffles between being stalely predictable and taking confounding narrative leaps. The construction of plot and dialogue is shoddy.