Alright **** this:

Is your license plate rattling?

What specifically is rattling?

Without knowing, we can't make any suggestions.

Put some weather stripping behind the bottom of the plate, ensure your entire bumper is secured properly, adjust your trunk latch, prop open the vent which doesnt prevent moisture from getting in since it doesnt create an air tight seal.

I've done all those mentioned above and now my REAR WINDSHEILD is rattling.

I'm fairly certain you can't fix that.