Can’t answer the first, but there are two screws…
Ah yes, so there are, I’m clearly going blind.
So I’m guessing you have to clamp the knife in the low-angle adaptor first, then clamp the adaptor into the main jaws. And the main jaws will be exerting extra force on the adaptor’s bottom screw because not only is that screw providing leverage against the top screw (like the main jaws do) but it also has to contend with the main jaws clamping down into the adaptor. Poor little thing 🙂