Then she remembered; Paul and Minta and Andrew had not come back. She summoned before her again the little group on the terrace in front of the hall door, standing looking up into the sky. Andrew had his net and basket. That meant he was going to catch crabs and things. That meant he would climb out on to a rock; he would be cut off. Or coming back single file on one of those little paths above the cliff one of them might slip. He would roll and then crash. It was growing quite dark.
(Virginia Woolf, To the Lighthouse)

"He would roll and then crash" is at the past reference time and when we foreshift this it would be "He will roll and then crash."

If the original sentence were "He would have rolled and then crashed," it would not an irrealis, but just a back-shifted form from "He would roll and then crash." And it puts more psychological distance from the original probability. Is this right?

Or "He would have rolled and then crashed" is at the past reference time and this incident is known now invisible narrator’s present time (= invisible speech time?), so this expression is quite different from “He would roll and then crash”. Because the latter is just the future possibility at the past reference. Is this right?