I am not a CSS expert but the tweak epub function (as dwig suggests) works for me. I open the stylesheet and make changes to line height, style etc.
For big spaces between paragraphs I change the conversion setting for that particular book to not add spaces between paragraphs. Usually this works.
If it doesn't I look for weird numbers and explicit sizing. For example a line height in em I would change to 1.2 or sometimes even 1. (without the em)
Same with indent I change them to zero or delete the line.
You do have a font style italic in your first example? Change it to normal, save the stylesheet and preview the result if you know where it appears. Easy to change it back or hit cancel and start over
It is pretty easy once you have done a couple
takes maybe two minutes start to finish.
Helen
The nice thing about tweak epub is thatyou can change the stylesheet, save it and preview the epub it before rebuilding it. And as theducks pointed out you can narrow it down with the viewer.