Washington (AFP) – Testy at times, rambling and poetic at others, Johnny Depp has embraced a familiar role at his defamation trial against his former wife Amber Heard — the leading man. During three days on the witness stand, the three-time Oscar nominee has sought to convince a jury that the allegations of domestic abuse made against him by Heard are untrue and have destroyed his career. Lawyers for the 36-year-old Heard have hammered away at the 58-year-old Depp’s history of drug and alcohol use in a bid to undermine his credibility. The “Pirates of the Caribbean” star has mostly kept his c…