Did any of those changes fix the spacing problems?
I can understand not wanting a user to change something you’ve worked hard getting just right. In the world of paper books, once it went to print your work was there for all to see. Electronic books is a slightly different mindset; the “artistry” is getting the product to look good across multiple devices (screen sizes, orientation, hi-res color vs e-ink gray scale) and taking into account the reflowable nature of the text.
I just got a book on Amazon that wouldn’t even download to my older e-ink kindle, so I had to buy a newer fire tablet. $50 for a newer tablet that is still excruciatingly slow kinda upsets me to begin with… but when I open the book I find that the publisher basically made each page an image … I couldn’t change anything… now, I know a guy (definitely not me

)that has worsening vision and MUST be able to change the font size just to be able to see the words without wearing huge glasses. When you change font size too much, then large margins become an issue… I had to return the book and gave a bad review, not because the author did a bad job, but because of the formatting decisions they made. I hope they fix the book - and I’ll update my review if they do.
As for the “error” Jon mentioned in your css, it was an extra { … some apps/devices will totally disregard the entire css file if even a single error is found (which is against the standard). There are websites where you can validate your css for errors… Sigil has a built-in function that sends it to get checked. I think it was just a copy/paste error since your full css copy didn’t have it in there.
Also, you certainly do not need to have the text-align:justify in your book. I’m sure you’ll appreciate that, historically speaking, text that isn’t “justified” was considered unprofessional - something about how long it took typesetters to figure out proper spacing, or some such… Today it is simply a preference - some like it, some don’t - and when you can switch between left/right/justified with the push of a button it’s not so much a “professional” thing anymore. As a matter of fact… since you said that ALL your text was right aligned, I would recommend not having the “justify” in there at all, and putting the right align in your css for that particular class.