First, you look fine AS IS!

Given that, everything else is just some tweaking. I agree the metal should match. It would probably be easier to get silver (or nickle) buttons than change the rest of the outfit.

You've put together a non-traditional formal look. I like the sporran you have for it.

I do echo the Wizard about the hose, though. Cream just doesn't quite fit. Maroon or White I think would be your best bets with that jacket.

Oh, and a waistcoat would be too much (in my opinion)

Congrats on a great look!