For trying to see the snake incubus, a couple of notes.
I did the things that Hereno said and didn't see it, in my first several attempts. There seem to be two problems in showing the image. First is setting up Allison so it is what is going on. This means getting the right response of Lorelei during sex, which are the parts that Hereno idientified. But then I got the right response from her and didn't get the image. After some fiddling I think I figured out why, I was generating too many other dream sequence possibilities (max seems to be four) and the incubus was not being shown (either due to random chance or lower priority). So my suggestion is to cut out the other edge case things that can generate dream options. For me this included not pointing out the blonde in the window, not flirting with Emma, limiting options with Renee and Dante, not getting Allison's libido (exhibitionism?) so high that she's going to be a stripper (this seems to have a very high priority in images shown), etc.
You can only get one pendant image in the dream sequence, not more. (You could get none.) I believe the space snake counts as a pendant image for this purpose.
So I suppose you're right that your character needs to be on an MC path (as opposed to a good boyfriend path) to get
any pendant image, and then I guess you need to make sure the space snake has prio over any other pendant option (although I believe that it does automatically).
Yes, you can only see a max of four images in the dream sequence, and you may see less than that, including zero. But only a max of one pendant image.
Also: do not try to see the space snake.