Good point. But the word "need" is also used in the sense of "strong craving". And strong cravings can be selfish both in regard to what is craved and in regard to how the craving originated. For example, someone starts going to expensive designer shops and comes to need the attention and flattery of the sales people there. Similarly, gamblers may need the next thrill, drug addicts the next fix, and so on. In such cases the word "need" does not imply a desire that is natural and important.
Because you take a position to be something one can act on, I interpret this in the sense of "commitment" or "disposition". So suppose a person has the deliberate disposition to "fix" student grades whenever he is offered $100 or more to do so. (This might be a professor or an administrator or a person with access to the university's computer system.) Surely this is an unethical disposition, that is, a disposition that one ought not to have, and the person so disposed is typically unethical on account of this disposition even if he never engages in any unethical conduct (e.g., because he is never offered a sufficiently large amount).
It's different with emotions because these cannot be simply willed away. It is problematic, then, to characterize a person as unethical on account of an emotion that she just finds herself having, without choice. Still, we do have ways of influencing our future emotions, and there are surely emotions that we ought to try to diminish or eradicate (e.g. disgust for people of certain skin color or sexual orientation, which can be overcome by seeking friendships with some such people). And one can then say in a temporally more extended sense that certain emotions and those who have the are unethical: in cases where one could and ought to have rid oneself of them.
Still, the basic response is the same for positions and emotions. There are three different entities up for moral assessment here. First, there are the positions and emotions themselves, which were the subject of your query. Whether they are unethical is entirely unaffected by whether the person who has them acts on them or not. Second, there are the actions motivated by the position or emotion. These are typically unethical; but if the person having the position or emotion in question never acts on it, then there are no actions to assess. Third, there are the persons themselves. Consider two persons who, otherwise equal, are disposed to fix grades for bribes of $100 or more (as described above), with one of them receiving and accepting several offers while the other receives none. Should we say that the former is more unethical than the latter because he had the "bad" luck of being offered sufficiently large bribes? This is the position Bernard Williams takes (in Moral Luck) and it is also the position implicit in the law (if the assassin's bullet is miraculously stopped by the intended victim's cell phone, then the assassin will receive the lesser punishment for attempted murder). On the other side, Immanuel Kant holds that luck can make no difference: that persons should be morally judged by their dispositions alone. Thus, the person less reluctant to be bribed is (other things equal) the more unethical person even if his counterpart accepts many bribes while he himself (for lack of opportunity) never accepts a single one.
Nietzsche and Camus come to mind. They don't exactly address emotional apathy as a philosophical problem. But they both develop philosophical positions that, in quite different ways, combine intellectual argument with emotional engagement. You might have a look at Nietzsche's Thus Spoke Zarathustra and Camus' The Rebel.
What is it to keep one's emotional reactions in proportion? There is a philosophical issue here that seems worth raising: emotional reactions are not simply sensational reactions to the world, they can be cognitive reactions too. Emotions can sometimes tell you things about the world that one's beliefs aren't registering. Perhaps your upset about the argument with your sister contained a cognitive response that was appropriate to the scale of the argument with your sister, in which case the emotional content in itself should not be changed by the thought that there are many situations in this world that would be infinitely more upsetting and difficult to bear. The advice that one should keep one's emotional responses in proportion - making sure the cognitive content is correct, if you like - might sometimes require one to let it go, but equally it might require one to stand by the upset and conclude that the argument one had this morning was indeed really upsetting. If so, one needs some other way forward than remembering how much worse things could be - talking it over with one's sister or whatever, explaining why one was so hurt, asking if she felt the same, and so on. Keeping emotions proportionate to the facts cuts both ways.
A very nice classic essay on this question is "The Conscience of Huck Finn" by Jonathan Bennett. I think you'll find it congenial and responsive to your second and third questions especially. I found a version on the internet: