When dealing with a relentless bully, what’s a young boy to do? In Douglas Lyons’s new musical, Beau, now running at Theatre 154, sixth-grader Ace Baker (33-year-old Matt Rodin credibly portraying a teen) manages to placate his tormentor, Ferris (Cory Jeacoma), with a daily tribute: a single cigarette pinched from his mother’s purse.