To sort of bring this back to where the thread started, unfortunately I have not had time to read further into the Apion material to see what is implied about Apion's views of the gods, rather than of the people he was criticizing. I would think if we saw clear indication that Apion held "the gods" to be active and engaged in world affairs, then that alone would rule him out as an Epicurean. On the other hand if active engagement is conspicuously missing, and his references were to the impiety being an insult to the gods' blissfulness, then that would weigh in the other direction.
I would think that there is a significant chance that we might be able to glean some of that from a discussion of Apion's charges of impiety, but unfortunately I still have a lot of reading to do.