1 seems a bit odd. You could argue that the Argument from Mind Design Space Width supports it, but this just demonstrates that this initial argument may be too crude to do more than act as an intuition pump. By the time we're talking about the Argument from Reflective Stability, I don't think that argument supports "you can have circular preferences" any more.
That's exactly the point (except I'm not sure what you mean by "the Argument from Reflective Stability"; the capital letters suggest you're talking about something very specific). The arguments in favor of Orthogonality just seem like crude intuition pumps. The purpose of 1 was not to actually talk about circular preferences, but to pick an example of something supported by largeness of mind design space, but which we expect to break for some other reason. Orthogonality feels like claiming the existence of an integer with two distinct prime factorizations because "there are so many integers". Like the integers, mind design space is vast, but not arbitrary. It seems unlikely to me that there cannot be theorems showing that sufficiently high cognitive power implies some restriction on goals.