Nice work and you have found all the problems with fitting the skirts.
The original Ford skirt fitting clips for the bottom are very brittle. Most will snap when fitted due to the age of them. I made a change to the clips for mine and made them thicker and added a built in nut so they screw on.
The top on the skirts are normally just riveted to the sill.
The front skirt section is very difficult to get on and off with the Ford brackets. Yes you can snap the brackets or the skirt section. I also changed the brackets on mine so the are slightly further from the wing when mounted. This allows the skit to come off without breaking anything.