MacKeeper is malware that charges you money to mess up your computer. You should remove it and never install it again.
Repair Permissions is useful ONLY when Apple-Installed Applications refuse to open. To do routine maintenence use ( Repair Disk ).
Except for rendering, working with Video is an I/O problem. Most of your drives appear to be slow antiques, and you can get a new fast 1TB for under US$100. You should have your Boot Drive separate, with only System, Library, Applications and the hidden unix files. All other files should be moved off to other drives.
When editing, you should have separate Source drive and Destination drive, and neither of those should be the Boot Drive.