Can't disable "Press the Option key five times to turn Mouse Keys on and off"
Change the value of useMouseKeysShortcutKeys to NO in 'com.apple.universalaccess.plist'. I believe you will find the files in ~/Library/Preferences/. When you're done, don't forget to reboot ;)

Also, you can do this via Terminal by typing defaults write com.apple.universalaccess useMouseKeysShortcutKeys NO and pressing enter. You may need admin rights to do this.