I broke down and did a clean reinstall of Firefox and holly mackerel, it's lightning quick now. It's been a PITA to get it set up like it was. When you install and uninstall add ons and other things over the course of several years, your profile folder will get filled with garbage I think. I've had a problem with Firefox pausing a lot, especially video playback, and it's mostly gone now.
If you ever do this, just an FYI. Firefox stopped using the bookmarks.html file for storing them. To save your bookmarks, go into the bookmarks menu and click on the import/backup button. I lost all my bookmarks at first but got about 90% of them back from my disk imaging software.