Autistic youth can't login to Facebook to fix page

my son is 21 and just lost his best friend from childhood from a Facebook page Police had posted bad information about him. He created a Facebook years ago and can't remember the password or other information for his gmail account, plus his phone number has changed so he can't login to Facebook. The Police posted wrong information on his IQ and Diagnosis and 2 old friends won't return his texts as they visited his Facebook and said he is too weird.... I have tried to re-set his gmail password with another e-mail account but it won't work. He's had enough challenges thrown at him, but having a Facebook page wreck his chance at a friend is terrible. Is there any way to change his settings?