EK do give some leeway if you're just short of a tier, but 500 miles might be stretching it a bit. If you're future travel with them is likely to be in Business, there aren't many benefits that Gold would bring that you don't get in Business Class anyway.
Chauffeur drive in Business as well as First, although there are some "odd" rules within Australia from what I've read. Hopefully someone can clarify.
Lounges available to you wherever EK have them. Partner Lounges elsewhere. Transit security in DXB - no customs - not sure about MEL.