The only time he has provided anything close to specifics is when he has referred to the accusations of grooming a 14-year-old. If those accusations cannot be proven, then he's potentially got a case against anyone who made the accusation. The question then becomes, who made those accusations? Can he demonstrate that any of the seven made those accusations publicly and with malice? Remember, defamation would require that a person make a claim that is untrue or that they cannot prove is true, made with malice aforethought.
He cannot file a credible civil/criminal claim for statements made about him that he has confirmed to be true. He has denied that he groomed a 14-year-old or that he had any sort of sexual encounter with a 14-year-old girl when he was in the UK. Aside from that, he has admitted to lots of stuff. He cannot win a case against any of those claims, nor would a judge allow him to base a lawsuit on the definition of "regularly" and how it applies to his admitted actions.