I'm relieved you've found the source of the metal filings. That safety wire is important, so you've just saved yourself from future problems, if the bolts come loose.
As for the plate behind the clutch, my understanding is that it is moveable so that it centers on the gearbox shaft. Once centered it needs to be tightened firmly in place. if it's loose it will start to rub on the shaft and worse.
Ditto...The plate should be able to slide back and forth relatively freely..As the hole in the plate is circular and the back of the clutch sleeve is circular there will only be a 'point contact' anyway and if the plate is free to move there won't be any contact pressure on it either ...Ian