I haven’t mentioned this before, but my degree is in Art History, of all things, and in my opinion your analysis is excellent!

It’s almost as if the two areas of the painting should be labeled “incorrect” and “correct.”

The retablo adheres the to standard iconography (from wikipedia):

An ex-voto requires certain elements in order to be considered part of the votive tradition. They are made as a way thanking the gods for protection in precarious situations. These situations could be returning a lost family pet or overcoming an illness. It is a physical way of thanking them for a miracle or an act of kindness. They must display humans physically doing something. They must include divine images, like saints or spirits. They must also have an explanation of events that occurred. The explanation must include the date and location that the event occurred.

But notice also how the cone of ‘green energy’ illuminating the ‘alien’ is matched by a parallel dark green cone, atop which the saint hovers on his own cloud-like ufo.

Even the saint’s cloud’s shape is matched by a similar - though inverted -outline of stars over the cantina doors.

Are these parallels merely coincidences, an attempt by the artist to covertly subvert the penitent’s view of the ‘martian’ as hostile, or indicative the artist has hit the old mezcal once too often himself, with similar but more pronouncedly spiritual results?