I am almost your exact same size but ride a Specialized in a size 54. I think my bike is a tad too big but not bad. You look fine to me in your photos but the one thing that seems off is a well set back seat post that puts you quite far back. A seat post with less set back will move you further forward and this in turn may mean a longer stem would suit you better. However, this is almost all speculation because until you actually are able to ride the bike, there is no way to know if it is a comfortable.
On the rear mech, it seems someone screwed up.