So I suppose I'm lucky to be getting any output at all (see the filler.prn.txt file attached to my original post). Unfortunately, iTunes is one of the many programs that doesn't have a "save as text" option - which is the shortcoming that caused me to start using the "Text Only" print driver in the first place. I guess I'll have to continue to hand-edit out the extra garbage that the "Text Only" driver generates - unless I (or someone) can come up with a way to automate that editing process.