Sorry. I still don't have it.
You can DOUBT something, but you can only be DOUBTFUL ABOUT something. I can't get past that in your sentences (subjunctive aside).
"Whether" introduces the idea of a choice. It doesn't seem to make sense to doubt a choice -- unless it be the correct result of a choice.
"Doubtful" and "uncertain" do not quite mean the same thing.
I continue to be puzzled.
I'm sort of okay with "It is doubtful whether (or not)...
But I am not okay with "I am doubtful whether...
Not sure why. Maybe I am too old-fashioned with my English for a " Contemporary English Dictionary". For example, I do not accept "As far a the grade..." without including "is concerned".
I agree that we are digressing. Bring me back to earth, and explain how this effects the syntax of the sentence in question.
I meant "as far as a grade (is concerned)...
You know, I may not be smart enough to follow my OWN conversations. I am confused. Can we go "back to basics'?