bq. In a perfect world, I would like my CSS to be loaded after all my page’s CSS and not before. Otherwise my page’s CSS overwrites a few of my userStyleSheet changes.
This not the way user stylesheet are defined, you can have a look at the constructor of CSSStyleSelector for the details.
If you want to impose your stylesheet on top of the document's style, you will have to set the style directly on the elements with the attribute "style" (you can do that with QWebElement via QWebElement::setStyleProperty()).
That start to be a bit hackish I have to say, and this might cause multiple layout of the page. I can't think of another way right now, if you are aware of a WebKit port doing otherwise, you can look at how it does that.