1 - As inoculation against the idea that humans are alone in the universe, and that we therefore occupy some kind of special and supernatural focus of existence.
My take is that Epicurean philosophy posits other world-systems, and that's where the "humans are not alone in the universe" would come from.
a slippery slide toward all sorts of mysticism
The slippery slide to mysticism and belief in the supernatural comes from a willingness to see the universe as not completely material or natural with no need of something "above nature" i.e., super-natural. The thinking of "This can't be all there is" is the beginning of the slippery slope.
Contemplation of the nature of a truly blessed existence - one which even though "godlike" must act to sustain itself - is similar to Epicurus' views of reverence for men wiser than ourselves. It's an important aspect of our own drive to use our lives in the most pleasurable way, and not to settle for less than what we are capable of obtaining.
Again, I don't see the god as "acting to sustain itself." The god's existence should be effortless and pain free. Attributing effort to the god robs them of their
Letter to Menoikeus: "You, Menoikeus, believe everything about which a god is able (δυνάμενον) to preserve (φυλάττειν) its own imperishability and blessedness for itself. Do not attribute anything foreign to its incorruptibility or incongruous with the blessedness of the god!"
φυλάττειν (phylattein) "to guard, maintain, preserve, etc." or "to beware of, be on one's guard against, avoid a thing or person"
δυνάμενον (dynamenon) "being able, capable, strong enough to do, can; have the power to"
I take that φυλάττειν as implying that the god avoids anything that would change their incorruptible or blessed nature. The god avoids anything that would go against its nature.
How can anyone contemplate the nature of a truly blessed existence if no one knows what a truly blessed existence is? Again, it's an exercise in futility. It's nothing more than: I want a truly blessed existence to be like x and y because I feel good making x and y a truly blessed existence. Gods are not needed for us to establish how to live our lives. We can do it with experience and course correction.
This is exactly why I see Sedley's position on the god/divine so interesting. I think it's relatively easy to contemplate "a truly blessed existence" and that Epicurus spells it out: A mind free from trouble and an ease of use of the body without any effort or pain. That's it. From my understanding, that conception of "what could be" is the exact nature of blessedness, of being "makarion." Mortals can never achieve it completely, but we can contend with Zeus if we make the effort to remember what we *can* achieve in this fragile, mortal life. I would completely agree that "we can do it with experience and course correction" as we go about living our lives. The idea of a god floating in the intermundia with no world for it to stand on like some preserved specimen floating in a jar of formaldehyde holds no fascination for me. What does is the idea that I - a mortal human being - can imagine, can have a thought experiment about *my* idea of a blessed life - my "godlike" existence - and work toward that via "experience and course correction" and making choices based on those lived experiences and thinking about consequences.