prepping to paint--worries about insecure underlying paint
I am preparing to paint an interior bedroom door and trim. I am sanding with a random orbital sander on the door. There is a little bit of an orange peel texture (I prefer smooth), and I also feel that I should sand because I tried a test I read about on Family Handyman to test whether your underlying paint surface is sound--lightly scratch an "x" with a razor blade, apply duct tape, pull off, if additional paint is removed by the tape, you have to remove that layer of paint. This door did fail that test. I sanded with 80 grit. After that the door felt smoother, but the top coat of paint seemed to be peeling a tiny bit. Then I sanded with 100 grit. Then I noticed that what was left of the top coat could be scratched off very easily with light fingernail pressure. I have not done a whole lot of painting--yet--but I have a bad feeling that painting over it will not last too long.
I've had a similar experience with the trim around the door. I used 80 grit sandpaper on the trim to remove previously sloppiness in painting. I removed two coats in a spot, and paint peeled on the surface at a right angle to the trim that you look at when facing the door. I sanded and feathered this, and I hope it will hold up, but I am not confident. This is a 25-year-old house and I believe these are the original doors. Not sure though.
What are my options?