If + simple past/continuous simple past/past perfect + would have

The old man sank his face in his hands. “God help me!” he cried. “But I would not have let the young man come to harm. I give you my word that I would have spoken out if it went against him at the Assizes.”
“I am glad to hear you say so,” said Holmes gravely.
“I would have spoken now had it not been for my dear girl. It would break her heart–it will break her heart when she hears that I am arrested.”

The Boscombe Valley Mystery, short story

Hi. The context is that the old man was the real murderer but the young man was wrongly charged with murder instead of the old man. The young man was going to be tried by the Assizes. Holmes invited the old man to his apartment and identified him as the murderer.

I previously asked about it here.

https://forum.wordreference.com/threads/i-would-have-spoken-out-if-it-went-against-him-at-the-assizes.3622865/#post-18458252

http://forum.wordreference.com/threads/if-the-new-book-went-popular-i-would-have-bought-and-read-it.3623463/#post-18460841

I was told in both threads that in the underlined sentence,“went”, “were going” and “had gone” all work well in the if-clause.

In the second thread, I tried to make up a sentence and its context working in the same way as the Holmes example and failed:

(Sentence made up by me) If XXX published the new book, I would have bought and read it.?

So dear teachers, how do you think of the two examples? Do you think “went”, “were going” and “had gone” all work well in the if-clause in the Holmes example? And why, in your opinions?

And could you give me a more common and general sentence that works in the same way as the Holmes one (where either simple past, continuous simple past, or past perfect is fine in the if-clause )?

Sorry if my post is too long.

Looking forward to your comments.

Thank you in advance.