Ix-- The attention-based 'off switch' sounds similar to my experience of HPPD. Mine is pretty moderate, but mostly shows up when I'm tired, stressed, or otherwise unfocused. I like to think of it as visual tinnitus-- the brain, for whatever reason, doesn't filter out (or perhaps generates) non-sensual perception information that winds up in the conscious experience of sight. Using focus to reduce one's experience of it may well be a learned skill, and as such would require practise. Driving would be a good, albeit unsafe if the perceptions are intense, way to do so: it is a very visual task, and one that requires a fair bit of attention, at least while learning. Perhaps reading (a paper/e-ink book, not a screen) might help as well? Focusing on a relatively visually bland stimulus, but one that nevertheless has a lot of information that requires attention to extract, might pull your attention away from the perceptions?
As far as DP/DR goes, that's (from my experience at least) more tied to anxiety, and I find that they act as a trigger for increased HPPD, rather than the other way around. YMMV of course.