I received your file, thanks.
Here's an easy way for you to populate your Total Tracks and Total Discs fields.
I'll assume you've already created Integer fields called Total Tracks and Total Discs. Add those to your file list view, so you can tag them (of course, you could tag in the Tag Action Window instead of in a column).
Select all the files you want to update with these fields.
For Total Tracks, edit the cell for Total Tracks with F2, and enter the expression:
=listitem(tag(Track #),1,//)
and press Return. For Total Discs, use this expression:
=listitem(tag(Disc #),1,//)
That's it. Note that the Tag() function is slow, since it has to read the actual raw tags from disk, so only use it to do this type of assignment (in other words, don't use it in a view generally).