PortwestS843 Workwear Adjustable Safety Tabard

I'm a size 10/12 only 5ft 2. Would a small/med be big enough or do I go large.

Does this run wide across the shoulders?..I have a similar tabbard but the neck hole is so large that the shoulder straps fall off my shoulders.

is it Matt black or a shiny material?

Are they Stain resistant to bleach.