They can restrict official trading, I thought they already did something like that before, maybe not. Besides, market is mostly made by large players, what people can trade in the banks will make less of an impact.
Yeah, "percentage points" is used to refer to a difference between two percentages.
For example, let's say some company previously held 25% of the market, but grew and is now holding 50% of the market. The company's market share actually doubled in size, which we could call an increase of 100%. Or, looking at it another way, because they grew from 25% to 50%, you can call it an increase of 25 percentage points.