The true/false binary is too limiting as a response to such a question because the answer is not binaric, but I went with true because the philosophy which inspires it is mostly true. Though that school of philosophy deals with too much and too little of a trait!
(By the way, you may find the philosophy in question - Aristotelian virtue ethics - fascinating! It's my favourite, and is easily applicable to modern life.)
Aristotle argues that most traits in excess can be bad, and that we should instead strive for balance. Think of positive and negative extremes as weights existing on a set of scales. For instance, courage. Too little, and you are a coward. Too much, and you are reckless. But if you balance the scales, there lies true courage.
I'll try to apply this to your examples.
Rudeness/Bluntness: In many ways, rudeness is honesty taken to an extreme. You're not wrong in suggesting assertiveness either, since you need that in order to be truly honest. But, if a person has too little of either, they become a doormat who can't be honest in voicing their true feelings about something.
Jealousy: The word 'jealousy' has two meanings - the desire to have what others possess, and the desire to guard what belongs to oneself. (We really should have two words!) Both meanings stem from selfishness, and indicate a lack of generosity. If a person is overly generous, they may ultimately undermine their ability to maintain their own livelihood. They are also easily taken advantage of. If they are not generous enough, often because they jealously guard what is 'theirs', they become greedy, and through this, undermine the livelihoods of others.
Cruelty: Cruelty is the opposite of kindness. Too much kindness, you can again be easily taken advantage of, to the detriment of your own wellbeing. (Notice the pattern here, that tilting the scale too far to one side typically harms the self, while tilting it too far to the opposite typically harms others.) Too little kindness, however, makes you cruel. (This is treating cruelty in its passive form. Active, deliberate cruelty done for pleasure is...)
Sadism: Sadism and cruelty are twins. While cruelty can be passive, or at least emotionless, sadism is active and deliberate cruelty inflicted for pleasure. So I would argue that sadism is merely the deliberate embracing of an imbalanced extreme (cruelty) for personal pleasure, and therefore is on the scale of kindness.
So, to summarise, the traits you couldn't find answers for within the framework of the question you posed were because they are symptoms of a trait turned down, with the exception of rudeness. But, while they may not fit neatly within the question you posed, but they do fit within the philosophy of virtue ethics, which is the philosophical 2300-year-old bedrock inspiring questions like these.