The sad--but honest--news is that there will be no easy automated process that will work for all 350+ of your books. The good news is: once you start rooting around in the CSS and html, it will become easier to spot patterns and methods that people use to put their epubs together. It will get increasingly easier to achieve exactly what you want with practice. But I would never attempt to "fix" 350+ epubs... I only attempt to fix the one I'm reading right
now.
