I was recently staying with my family near London and one of my relatives used the idiom 'that's above and beyond the call of duty' several times over the course of a few days. You can also just say 'that's above and beyond'. This idiom means that an action is more than is normally required of a person - it goes beyond the scope of their normal responsibility. For example, if you have an important project at work, and in order to finish it you work on weekends for several weeks, this could be considered 'above and beyond the call of duty'. 

Sudeep, yes, white is normally a colour associated with peace, but I think the point of the proverb is that crows are not supposed to be white. They are expected to be black. A white crow would be an albino crow that might not be accepted by the other crows.

It's the same with sheep. The most common colour of sheep for farmers to own is white. If a black sheep is born, the farmer might be displeased by its colour, because the wool of a black sheep is not prized as much as that of a white sheep. 

Natalia, are you sure about the first one that it mostly has a negative meaning? Why I asked it because whenever the color "white" comes, it mostly indicates good or peace(e.g. a Dove is considered as a symbol of peace as its color is white). I also googled it and found that it's a Russian and Ukrainian idiom that mostly means a person who doesn't really get along with others but s/he does have anything bad towards others. So, if what I said is right then, I found two idioms(you can use in a positive sense) that may fit your first one:

- Sticks out like a sore thumb.

- A square peg in a round hole.

2- To cast a shadow on somebody(someone's heart) is itself an idiom. So I think you can use it.

3- Maybe, A man of virtue

5- Maybe, A man of his caliber.

7- Another one maybe, to open Pandora's box.

Elizabeth, the first source that I looked into asked this question but said "white crow" is not like "black sheep". That's why I thought it might be a positive expression.

https://forum.wordreference.com/threads/a-white-crow-vs-a-black-sheep.1951878/

But in the second link, it says it means black sheep. 

tywkiwdbi.blogspot.in/2011/04/black-sheep-white-crow.html

Now, Natalia can say how they use it(in a positive or a negative sense).

1. A black sheep. Specifically, we say "s/he is the black sheep of the family". 

2. Not sure.

3. Not sure.

4. If something is very easy to do, we say it is "a piece of cake". However, you said your proverb is more about understanding, not doing, so I'm not sure if it's the same one. Maybe it could be "as easy as pie" or "as easy as one, two, three".

5. Perhaps this one is the equivalent of "to dig deep". 

6. We say that something "comes out of the blue" and this means that it is unexpected. (The "blue" means the blue sky). However, it can be either negative or positive.

7. Not sure of exact equivalent. We could say "there's no turning back now". This means it is too late to undo what has been done. We must continue with this situation even though it has become negative. We could say "trouble comes in threes" which is a superstition that if one bad thing has happened, another two bad things must also now happen. We could say "we / you have opened a real can of worms" which means that you are dismayed to find that you have uncovered a terrible secret and now something has to be done about it.

8. Money can't buy happiness.