Virtue is about wanting right and good things, not about being particularly good at thinking.

Duties concern things that are voluntary. I do think that if you have a moral duty to bring me back the book you borrowed, that implies, roughly, that your doing so depends on your wanting to do so: if you want to bring me the book, you will. This is not the case if you are stuck at some airport due to a snowstorm, far away from me. This, however, is not the same as "ought" implying a metaphysical "can".

Sometimes we deliberate - for example when we plan a long trip or - if we are not math wizards - when we solve long division problems. However, if we deliberated every time we acted we would never get through the day. Most of the time, we act for reasons without deliberation. I am not just talking about cases of simple, habitual action, like brushing your teeth, but also about more sophisticated action.

"Externality" is a different phenomenon from akrasia and doesn't always come with it. The set of desires and actions from which one feels alienated isn't always the same as the set of desires and actions of which one disapproves. It has been pointed out that you can disapprove of something inside yourself but still experience it as yours ("damn it, here I go again!"). In addition, you can approve of something inside yourself but feel like it's not yours ("when the emergency sirens went off, it was as if someone calmer and more reasonable took over and knew just what to do").

I think that if your tenure case depends on your proving what you thought was a mathematical theorem and the proposed theorem turns out to be false just before your tenure decision, and you want to get tenure very badly, there is a sense in which it's perfectly understandable and reasonable of you to wish the proposed theorem were true and provable, even if it's logically impossible for it to be.

Suppose a student of mine writes in her exam that "morality is completely relative to culture, so nothing is absolutely right or wrong. Because of that, it is absolutely wrong to be culturally intolerant". This student, if she believes what she writes, believes a contradiction. She ought not to believe the contradiction - it's a basic epistemic norm. This is true even if she can't avoid believing it - no amount of studying will show her the light.

Moral virtues and intellectual virtues are very different from each other, and moral virtue has to do with motivation, not cognition. Moral virtue requires a human level of intelligence, but it doesn't require that one be an intelligent human.