Yes, but remember you asked about someone who had a deep and all-encompassing disagreement with the field in which they were studying, not someone who merely disagreed with the dominant paradigm of their time.
Yes, but again, that is different. Could you disagree with the fundamentals of Marxism while calling yourself a Marxist scholar?
You proposed someone who disagrees with virtually every single facet of their field. That's an extreme position, and I think that such an individual is unlikely to ever enter the field they so profoundly disagree with to begin with. But perhaps you want to talk more about individuals who disagree only with the dominant paradigm in their field? That's different from disagreeing with the entire field of study on all matters, great and small.