I wonder if you might find (or maybe you have) old techniques for etching aluminum in some old books from say, the 1920s-40s.
A lot of machine labels/placards were made from thin sheetmetals by etching away much of the surface to leave raised text and symbols (and some fairly small text at that). The etched areas were often then filled with paint for contrast. A lot of those etchings were brass, but I've found many smaller ones, such as those found on old power tools, which were aluminum.
I got the part about the reaction and the heat. If the resist had stayed in place (in a diluted or buffered etchant solution), you may have achieved results more to your liking.
When the resist has poor adhesion, any type of etchant is free to wick under the resist and migrate freely, essentially sucked in by the capillary action of the fine scratches.
There is a term in refinishing techniques that describes a problem that arises from using coatings that aren't properly reduced/thinned properly. When a coating is too thick to wet the surface properly, bridging occurs. Bridging is when the coating forms a skin on the work surface, but doesn't penetrate down into the valleys of the sanded surface. The result is air paths under the coating, and will lead to serious problems with subsequent applications of coatings (additional primer or paint). Bridging usually isn't a problem with aerosol rattlepaint, as there generally isn't a high concentration of solids in the product.. but it can happen.
The phosphoric etchant solutions I referred to are mild, and don't really attack the aluminum aggressively.. instead, they mostly just clean the surface of all oxidation. If the diluted metal prep were applied to a high polish/mirror finish, it would dull it slightly, but not pit or erode it. If a high polish finish were desired, the polishing would be done after etching.
There are primers that are called etching primers (aerosol or bulk), which I believe are intended to result in better adhesion, but I haven't investigated the actual process of their etching properties. I'd guess the etchant would be completely different than the water-based types I've used in the past, as the solvents need to flash and evaporate quickly.
I think I recall that you've described some electroetch techniques, but I don't remember if you had tried them, or were investigating them.
Have you tried to apply any of the laser printer toners as resist, by printing a mirror image and then transferring it to the workpieces? If an accurate image is difficult to produce, then omitting the characters and just cover the workpiece, so you could carve out the characters by hand (if that's your usual method). This process has been used for quite a long time for etching relatively fine detail printed circuit boards. The transferred toner adheres well, but it's also a very thin coating.
When folks here in RCM discuss rugged coatings, they often mention spray-on truck bed liner. I would imagine that the cure time is long, and workpieces might need to be coated well in advance. I haven't used these products, and at least one user has commented that surface prep isn't absolutely required, but proper surface prep nearly always improves proper adhesion.
Another product that's highly regarded as a good corrosion preventive coating is the line of POR coatings, so that may be another option.
Any material that's used for resist should receive the proper preparation of the surface. If proper application dictates that a primer be used, then the primer should be applied to a surface that's been prepared so that it will achieve maximum adhesion. Curing times for various coatings can vary widely.
The resist coatings shouldn't be lifting away from the workpieces because of minimal adhesion, or break down from moderate heat. Paint manufacturers test their products very aggressively for chemical resistance and durability, including elevated temperatures.
Before the nasty multi-part paint formulas (hardeners, catalysts), heat was the most common method of force-curing paints. Heat will dramatically increase the durability/toughness of common paint coatings. For home shop curing, a heat gun or even an incandescent light bulb in a small fire-proof (metal) enclosure will be sufficient. Of course, the sun also works remarkably well, some days.. and much faster with dark colors. The vapors should be vented outdoors thru an appropriate/safe venting syatem when primers and paints are applied indoors.