Robert De Niro and Paul Dano play a father and son who reunite after 18 years of estrangement in “Being Flynn,” and they approach their roles in such polar opposite ways, it's as if the actors themselves have been estranged, as well. De Niro, as the alcoholic, ex-con, would-be novelist Jonathan Flynn, is all delusional bombast; he insists everything he writes is a masterpiece, and his bravado barely masks his insanity. Dano, as Flynn's aimless, hipster son, Nick, may actually have some talent and insight as a poet but he's meandering between jobs, homes and girlfriends.