Talk to your local guitar store. The screws can be easily replaced, and would be quite cheap, so there's really no point in trying to clean them up, the effort wouldnt be worth it. As for the pups, you could probably take them out of the guitar and use a hard bristle brush with some WD-40 or similar product to get some of the rust off, this is availabe at hardware stores, just ask for a rust removing spray and the people should point you in the right direction.