Dude, moisture in oil ain't causing no rust. Not happening. Oil prevents rust, not causes it.

If there were enough moisture in the oil to cause rust, there'd have to be so much water it sat on top of the oil, and if there were that much your engine bearings would be destroyed.

You literally have holes in your hood where water can get to top of engine, but somehow you think the problem is moisture from the oil, not water through the hood.