I notice there are new versions being released that have nothing to do with the rendering issues. Why are you working on things that are not nearly as important as proper rendering?
I just had a look at the CSS for the eBook I'm using to check the app and the CSS for <p> has a bottom margin of 0. So there should be no paragraph spaces.
CSS for <p>
Code:
p {
margin-top: 0;
margin-bottom: 0;
text-indent: 1.2em;
widows: 1;
orphans: 1;
}