Yes, I agree with you. When I compare my native language with English - it's so funny. For example - in Russian lang we can say sentence, which consists of defferent words, And in English this sentence will consist few similar words. 

She said that the word 'contradiction' can be a possible alternate word.

I'm surprised to know that. I thought you were wrong and searched google but found that you are indeed right( or he is indeed right).

It seems 'fat chance' is a sarcastic way of telling that there is no chance.(say, 100% not possible)

But 'slim chance' is say, 99% not possible.

I would appreciate more insight into it.

I recently learned that 'oxymoron' is an insult in Australia, meaning "stupid". I forgot to ask her if there is any alternate word for that.

You have an interesting( funny :) ) collection there.

"Happily married" hahaha :) I wonder if any such couple exist.

“English is a funny language. A fat chance and a slim chance are the same thing”. -Jack Herbert