Do you think your ex may be a narcissist? Narcissistic Personality Disorder is a pernicious disorder, it will leave their victims with PTSD, paranoia and even health disorders. There is no cure because NPDs believe they are perfect, it is everybody else that has the problem.
If he is a NPD, cut all contact. Do not reason with him. Do not show he affects you in anyway. NPDs will quickly tire and move on to find an other victim.