Perhaps you could try and "comment out" the offending lines and see what happens.
Put 2 hyphens at the beginning of a line to turn it into a comment (so Applescript won't try to process it). Try this with the lines:
save document 1 (change to --save document 1)
close document 1 change to --close document 1)
If you try this, start with just one Quark file in the folder that you choose in the Choose Folder dialog box that comes up when the script first starts. If the script runs, the Quark file will be left open and unsaved, but perhaps with most of the work done as far as changing fonts goes.