No. Faulkner was interviewed multiple times after his arrest in Pakistan. A tiny sample of the interviews is used during the ending credits. All of them show Faulkner to be considerably more cogent and his speech far less affected by kidney failure.
A GQ magazine article attests that Faulkner discovered his kidney problems between attempts to find Osama bin Laden, and has a family history of polycystic kidney disease. Whilst renal failure can cause dementia and dementia-like symptoms, it is not likely that he was hallucinating and making a fool of himself in Pakistan to the extent that is depicted in the film.
Faulkner also has a criminal record including burglary and domestic violence that the film neglects to mention.
