Is there any software/add-on that have complete formula library, so I can easily insert any formula to MS Word?

Basing on the type of use it differs, If you use it for personnel works then Ultimate fits you or if you have Office works then Professional is Best for you.

Professional as it has a lot of flexible features within it!

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.