Talked to Dan Stewart
Ok, I talked to Dan today, sent him pictures, and we have a preliminary plan.
From what he's doing, I think he suspects contaminated primer somehow. He's sending a new quart to try. We shall see. He found that the color would lay down over the bare metal, but not over the primer, very odd.
I have put down some other paints over the primer, all seems well. Tough as heck too. Cheapo spray enamel over the Stewart primer seems VERY TOUGH.
As I suspected, I had tried about every reasonable, as well as some crazy permutations of materials, prepping, techniques, etc.