You are really doing an amazing job. I had a Fire! in similar condition that I got rid of in a trade to a fellow pinsider. I had the same exact issue when removing the mylar from mine.
It was the first time I tried taking mylar off and I was so mad because I was very careful and it peeled lots of paint anyway.
Fire cabinet art was originally screen-printed right? What kind of material are you going to print your replacement cabinet art on and do you do any kind of clearcoat over them after you apply them?
I've been thinking about repairing one of my game cabinets but always worried that a decal would "stand off" the surface too much and look goofy.
Keep up the awesome work!