Ah, that makes it much clearer.
What I would do is to move categories of things around so they fit best on what's available. I might move videos or music to the 1 TB drive, because those are the largest number of files that I want to stay together and I don't necessarily want them while I'm away. Documents would stay on the hard drive, because I'd be likely to want those on the go. Once you have that set up, use aliases or shortcuts to put links in the right places so it's easy to get to your drive from the normal folders. In other words, remove the Videos folder and instead replace it with a link to your external HD's Videos folder.
If I were you, I'd strongly consider picking up some more storage, like a ReadyNAS or similar drive. Right now you have 3 hard drives and if any of them fail you're guaranteed to loose some stuff. If you pick up a 2TB external drive for backups, you'll have to detach another drive to hook it to your computer. If you have a network attached storage device with redundant drives, your data will be much safer, accessible over your home internet connection and the storage will be (potentially) expandable.