Sure, let me try some specific questions.
I'll start with what I think is clear to me about Eliezer's views:
(1) Whatever moral facts exist, they must be part of the natural world. (Moral naturalism.)
(2) Moral facts are not written into the "book" of the universe - values must be derived from a consideration of preferences. (In philosophical parlance, this would be something like the claim that "The only sources of normativity are relations between preferences and states of affairs.")
I'll propose a third claim that I'm not so sure Eliezer would endorse:
(3) What I "should" do is determined by what actions would best fulfill my preferences. (This is just a shorter way of saying that I "should" do "what I would do to satisfy my terminal values if I had correct and complete knowledge of what actions would satisfy my terminal values.")
In this sense, morality is both "subjective" and "objective". It is subjective in the sense that what is "right" for me to do at any given time is determined in part by my own brain states (my preferences, which result from my terminal values). But it is objective in the sense that there are objectively correct answers about what actions will or will not best satisfy my preferences. I could even be wrong about what will best satisfy my preferences.
Have I interpreted Eliezer correctly so far?
(1) Whatever moral facts exist, they must be part of the natural world. (Moral naturalism.)
In a manner of speaking, yes. Moral facts are facts about the output of a particular computation under particular conditions, so they are "part of the natural world" essentially to whatever extent you'd say the same thing about mathematical deductions. (See Math is Subjunctively Objective, Morality as Fixed Computation, and Abstracted Idealized Dynamics.)
...(2) Moral facts are not written into the "book" of the universe - values must be derived
In You Provably Can't Trust Yourself, Eliezer tried to figured out why his audience didn't understand his meta-ethics sequence even after they had followed him through philosophy of language and quantum physics. Meta-ethics is my specialty, and I can't figure out what Eliezer's meta-ethical position is. And at least at this point, professionals like Robin Hanson and Toby Ord couldn't figure it out, either.
Part of the problem is that because Eliezer has gotten little value from professional philosophy, he writes about morality in a highly idiosyncratic way, using terms that would require reading hundreds of posts to understand. I might understand Eliezer's meta-ethics better if he would just cough up his positions on standard meta-ethical debates like cognitivism, motivation, the sources of normativity, moral epistemology, and so on. Nick Beckstead recently told me he thinks Eliezer's meta-ethical views are similar to those of Michael Smith, but I'm not seeing it.
If you think you can help me (and others) understand Eliezer's meta-ethical theory, please leave a comment!
Update: This comment by Richard Chappell made sense of Eliezer's meta-ethics for me.