Yes, both are correct usages.

Ending a Year, Starting another One

It is was time to look back and assess if we have achieved our resolutions said at the end of last year or not. Unlike most people, I can say "absolutely, yes". There is a simple reason for it. Because I did not claim any resolution at all. In my opinion, it is widely proved that less that 1% people get success in this question. So, why do we get frustrated just for promising ourselves something out of reach?. Probably, trying to be less ambitious and taking our resolutions in another season less busy than Christmas , it would be better to improve ourselves.

They indeed are all very similar. They also aren't used very often and I suspect if I went to my native speaking coworkers and asked them the definition of 'acumen' most would not know the answer :) But to answer your question. Acumen- generally refers to good decision making and skills. For example, the lawyer is known for his legal acumen. Acuity - is used in a more broad sense so that it can cover things such as senses or general wit and intelligence. For example, the cats visual acuity is much better than humans. Acuteness - This is even more broad and can actually be confusing since 'acute' can be used in math, describing a symptom or wound or a skill. Examples: The acuteness of the angle confused the teacher. The doctor analyzed the acuteness of the injury and determined it occurred during the car crash. The football players acuteness helped him score.

The Poor Girl

I’ve still been reading Joanne Rowling’s book titled “The Cuckoo's Calling”. This morning I read about Lechsinka. According the book she is young girl, a cleaner, who works in a home for very rich people. The author describes her as “short and very pretty in a pert, girlish way, with a rather flat face, a snub nose and Slavic eyes”. Another important her characteristic – “Eric Wardle had described her English as “crap.”” These are quotes from the book.
When Englishman Strike tries to speak with Lechsinka, she doesn’t understand very easy words, such as “detective” and “man from the security firm”. “Detective”, “security, “firm”, I think, these words have very similar pronunciation as in Slavic languages as in English. Even though that girl was really so stupid like Joanne Rowling wanted to represent her, such misunderstanding couldn't be.
The book doesn’t contain any information about Lechsinka’s native language (or I couldn't find). Because her name and “Slavic eyes” she was from Eastern Europe maybe. I was upset for Lechsinka. In addition “Lechsinka” sounds very similar with Russian word “lichinka”, which means larva, maggot or worm. Is it just coincidence?