Brilliant outline of the possibilities!
Epicurus thought of himself as a “Democritean” as a younger man
Yes, a very good fact to keep in mind!
he was a true historian of several hundred years of philosophy, and deeply fascinated by each thinker's arguments.
Yes, in On Nature, he is not just taking on Plato, but also Democritus and Anaxagoras (for example).
I agree there still may be a few dots to connect. I'll keep this post in mind.