Hey @troy,
I have a feeling you're doing something the hard way here.
To get the path of your backup file you really only need one line of code in an Execute a Shell Script action.
Find Today's FMP Backup Zip File v1.00.kmmacros (8.4 KB)
Macro-Image

I think I can do the same with mdls, but find is a tried and true Unix tool.
I'll fiddle with it a bit more later if I have time and gumption. (Found some.)
mdfind -onlyin ~/Dropbox/FMP/New_Server_BUs 'kMDItemContentModificationDate >= $time.now(-1h) && kMDItemFSName == *'$(date '+%A')'*'
I guess I'm done now. 
-Chris