Style sheet not being correctly parsed in Assistant (QTextBrowser-based)/documentation of QTextBrowser's CSS support missing

I've created a documentation set for our software and the .qhc files that are registered all include the style sheets from my HTML editor. If I open an individual HTML file, the style is correct, but when opened in QT Assistant as part of the QTHelp file (.qhc), I lose some of the formatting. For example, the title bar is set to a blue and there is no color in Assistant. If I zoom in a web browser, everything in the topic gets larger, but performing a Zoom in assistant, only the Header paragraphs increase in size. I have Browse arrows included in the header and there positioning is ignored in Assistant. I'm not sure if this is a bug or just operator error. I have gone through the QTHelp documentation, including customizing Assistant, but based on that I cannot figure out what I'm doing wrong. I should note that I'm the technical writer but have access to developers if needed. I looked for info on how the QTextBrowser browser used in Assistant parse's style sheets but haven't been able to find any as I was hoping to maybe modify my .css files to parse correctly. Any help would be appreciated.

The style sheets and collection file are attached.