Well.. I'm NOT familiar with wilwoods, but the some sets I saw came with brackets. And the accompanying discs are BIGGER than the EK9..
So can't really help you there.
As for drilling the center lug holes, yes, they do weaken the structure, as with everything else that gets a hole punched in them.. :P
But what holds the discs in place during hard braking is not those two tiny screws, but your wheel hub area and the lugs, which is why high horsepower cars/trucks tend to have more lugs.. 5 for cars, 6 for trucks, and up to 8 for lorries.. (O_o)