Cinnamon 75 Duster \

Rustoleum really never hardens, that is why if you paint something and set it in the sun, it turns to a dull white chauk, in a few months. Its oil based, with no hardners.
I bet you can still push your fingernail in the primer where it peeled.
You did an excellent job on that car, on a budget, I am not giving you a hard time at all, your car looks great, and the best thing is since you built it, you can fix it.
Roll up your sleeves and get it done.
I know what you are saying about it not hardening and eventually getting chalky. Have used lots of oil based Rustoleum for years. This was different... I think it said it was acetone solvent. Dried VERY fast and hard. Made it very easy to sand, but...
I will do touch-ups as long as I can to keep it looking good and then figure out what to do with it. If at some point I can afford a good paint job, ...it will go on the next one I build. LOL