Everything out of sync

Just in case, could you uninstall the audio booster, restart the computer, reduce the video playback quality and see if the problem persists?

If that doesn't work for you, you can always use this:
http://www.hecticgeek.com/2013/02/fix-audio-video-sync-save-permanently-avidemux/

If you don't need "cuda.kext", here's how you can uninstall it. (Wil involve terminal commands.)
https://devtalk.nvidia.com/default/topic/520257/uninstall-cuda-in-mac-/

I think I go through a very similar case. For me, every once in awhile when I watch a movie (MplayerX, VLC player, youtube, etc.), I get a hiccup which puts the audio and video out of sync. My situation is that the audio does some weird sound repeat so you might hear like "hello there, my-my name is Billy", and then the audio is off-sync because of the extra "my". I would have to pause whatever video im watching whether its on youtube or MplayerX for a few seconds to a minute, and itll resync after I unpause. I think it's a hardware issue on my part since this happened on Mavericks, and then still occurs on Yosemite after a clean install. Sometimes, the video would have some weird electrical sound or be muted for a second and then be off-sync instead of repeating words like "my". I've come to accept it for now since for me, it might be hardware or drivers issue...