That's always a tough case.. we've had them, too.
He's obviously disgusted with his current circumstances.
The clotting off and extended time due to that is even more frustrating. Have you tried heperanizing the dialyzer itself?
Perhaps allow him to have another staff do his tx. for awhile without making it obvious to the other pts. Maybe after a few weeks he'll see it's not "just you".
Sorry to hear about this, I know how frustrating it can be.. for the patient as well as the staff !