Acid releases cyanide -- to the air. Once released, cyanide is very volatile, lighter than air, and readily disperses. That is why, if you do a lacto-fermentation on some high cyanide containing fodder, the cyanide disappears and it becomes safe to
feed.
Second point to note is that in all the
Prunus seeds, the cyanide containing compound,
amygdalin, is contained inside the pit. You have to crack the rather hard hull of the pit open and get to the true seed inside.
So no, I don't think your salad dressing is going to be toxic.