This sounds like a case of checkrideitis.

I second the "I dunno" act. The next time you meet, explain how that as he gets closer to the checkride (ooohhh "checkride" that'll fire the nerves up), you're going to get dumber and dumber. Let him know that you're going to start acting like an examiner and be very quiet in the right seat, only jotting down the occasional note.

Then, on the flight, get it headed towards safe terrain and airspace, and shut up. If he asks, you can list what maneuvers he's to perform. But, unless imminent pain is about to occur, don't interfere. On the flight, list everything he does right, including looking for traffic. Once, when he does do something right, or makes a proper decision, you can challenge him, "Do you think that is correct?" If he asks back, shrug your shoulders, do the stupid look, and say "I dunno," and scribble something on your notepad.

On the postflight, you can tell him he knows what he did wrong, and list what he did right.

You can also suggest that if he doesn't know the PTS, then how can he know what he did wrong? Suggest he read the introduction as well, 'cause if he thinks one exceedance of a maneuver fails the ride, then he should fail, but for not knowing the PTS.

Other tricks I've used have included multiple flight lessons in a day, so the person didn't have their family and work life interfere with the learning and remembering; chair flying through a lesson, the student talking his way through it; refusing to fly unless the ground information was learned; and clipping the solo wings - very slowly and deliberately, with good-humored joking as it was done about my being a mother hen. Sending the student up with another instructor and even with the DPE has also worked.

Find the roadblock, and find a way around it.