Silicone is ideal for the covers, it keeps the water out better than a gasket on its own.
As for the brake, there should be a spring to keep pressure off the brak discs. When its all in place, the brass pucks hold the discs so they won't touch anything.
The cast lever should have a flat piece of steel under it from memory with a loop for the spring to attach to. This had another tab that was held in place by a bolt for the inspection cover.