Pea Coat Buttons

Question from J.F.

It’s currently very cold here, around 3°C (+/- 37°F) and I’m wearing my navy blue pea coat all day long. The question is, should I button all buttons down or leave the last one on the bottom unbuttoned?

New buttons for navy jacket..

Hey guys, one of my buttons on my blue Jacket broke when I was walking home and I don’t have a replacement. I decided to replace all the buttons to make it look more like a blazer than a suit jacket. I have a few questions.
I think I need 1.5cm buttons for the front-should I get the same size buttons on the wrist or go for 1cm buttons?
Two buttons on each wrist?
Thanks.