U.S. Polo Assn.Men's Classic Polo Shirt, Two-Button Closure Pique Polo Shirt, Summer Fashion Golf Shirt

Q: I would like to know the medium size in polo shirts chest size in medium ?

Absolutely and the medium size fits me.

Q: Why can't exchange this shirt for a 1X as this is way too big for my husband?

I don't know .. it depens of the rules about exchanging.

Q: I'm 5'6-5'7, 155 lbs, and have a slim body type. when it comes to polo shirts, i don't like anything loose. should i go for small or medium?

I would guess small would be too small and tight. I am 5'8", and 146 pounds and a medium fits perfect. I like the material in this shirt, and it is loose enough not to feel restrictive, but it isn't baggy. I bought my first one and then I got 2 more because I like them so much...it is my favorite polo shirt.