Unfortunately I can't remember how older software updates were presented from Sony.
My newer Sony TV, the updates download as a .zip fie which on the completion of downloading automatically unarchives to another .zip file which when created you transfer to the USB.
Once plugged in to the TV it begins the update process.
If you take the second .zip file and use an app like The Unarchiver (free download) you can see the contents of the .zip file, the largest of these is a file called payload.bin, this is the one with the update files inside.
Here is one more thing you could try, this is a very long shot but give it a go.
From the .zip file you downloaded and opened to the folder containing the .pkg file.
Click on the folder (the .pkg file must be inside), now click on File in the menubar at the top of your screen
scroll down a little and you should see Compress <folder name>, click on that and this will create a new .zip file
on your Desktop. Transfer this to your USB and then to the TV, see if the TV does anything now.
Chances are it won't but it won't do any harm.
