With some help from a coworker, the PrettyCSS validation works to our satisfaction on our CSS. It's a combined 78,000 lines spread across 200+ files. Now all that needs to get done is to write a command-line tool in order to plug it into our Git hooks. This will automatically validate all changed CSS as well as pretty print the results so we have a consistent look to our files.
It's good to get this work to a point where it is usable for a team of developers. I will get more feedback and potentially additional CSS declarations that need to get parsed as they will now be able to focus more on CSS3 properties (our older tool didn't support them).