Yes, it is rated for inland use I don't have the tag anymore or I would quote the class and rating but I remember double checking for lakes and rivers. Offshore I can't comment because I tossed the tag.
I'm 6'5 and 275 and even I needed to pull the adjustment straps pretty tight. Definitely made for a larger person.
I believe it would
This is a floatation device and should work well for a 180lbs. person. I am over 200 and this fits me well. I have not been in the water with it though, so I can't say how well it floats a person.