I would say that if you agreed to be a guinea pig you should remain a guinea pig
Seriously though, when you agree to participate in research you take on an responsibility to the science, and for that reason you should stay compliant with the research protocol. You got the free medication, counselling, and you got paid, so I think that amounts to an ethical obligation. Do what you can to validate the research and provide sound data, and keep in mind how it will help people with alcohol use disorder.
Have you asked the researchers if you can transition to Nal free when you're AF?