I can help you with your first question. Get some 0000 steel wood and some light gun oil such as Break Free CLP. Even 3-in-1 oil will work. Apply the oil to the slide and gently scrub it with the steel wool. Keep it wet with oil. Should take most of the rust off.

I would find something else to store it in. That foam might be holding the humidity and causing the rust. Just leave it out of the case or get a gun sock to store it in.

Keep a light coat of oil on it and reapply gun oil as often as needed. Check every month or so.

Here is a video on the proper cleaning of the SD9VE.