"And why were you so pressing that Sir Charles should (should-1) destroy your letter?"

"If you have read the letter you will know."

"I did not say that I had read all the letter."

"You quoted some of it."

"I quoted the postscript. The letter had, as I said, been burned and it was not all legible. I ask you once again why it was that you were so pressing that Sir Charles should destroy this letter which he received on the day of his death."

"The matter is a very private one."

"The more reason why you should (should-2) avoid a public investigation."

1）第一个should-1：主句带有形容词pressing表示人的情绪感情等之意，所以是推定式的should, 应该翻译成“居然，竟然”的含义吗？

2）The more reason why you should (should-2) avoid a public investigation 这句中的should有如何理解？

     这里的should是否和牛津词典：

why, how, who, what ~ sb/sth do used to refuse sth or to show that you are annoyed at a request; used to express surprise about an event or a situation （表示拒绝、恼怒或惊奇）

Why should I help him? He's never done anything for me. 我干吗要帮他呢？他从来没为我做过什么。 

是一样用法吗?   （只不过语序不同，why should I, 和 why you should）

如果是的话，那么The more reason why you should (should-2) avoid a public investigation.应该怎么样翻译才能带有表示拒绝、恼怒或惊奇的含义呢？