Do not mix Enamel with non-enamel Rustoleum paints. That's exactly what looks like happened.
I like the 2x Works with Plastic version of this brand. Do a white or gray primer (2x) and topcoat with the white gloss (2x).
Do all your gloss layers within an hour or so then don't touch it for at least 24 hours. Let it cure fully (up to 2 weeks) before doing anything else to it. Gloss will contain some additives that let it fill in better to achieve gloss finish and will take a lot longer than flat to cure fully.
As far as getting that off, you'll need to go to bare material. Any additional layers will give you the same result. Use Easy-Off oven cleaner to remove it easy. Wash, scuff, wash again. Hit with rubbing alcohol and let dry a bit and you should be ready to prime once more.