I can answer your question #2, at least! No, there are no grocery stores or shops nearby/ walking distance - the Southampton is really "away" from everything. However, it is REALLY easy to take the local bus system into Hamilton (or anywhere else you want to go), and there's a stop right at the hotel grounds entrance, from what I remember.

I didn't have a suite, but my recollection was that the rooms were spacious and very comfortable, and the entire property in fact was quite beautiful. This was in contrast to the Fairmont Hamilton Princess, where I DID have a suite, but really wasn't impressed much - greatly preferred Southampton. (And fortunately stayed there 2nd!)

I'm pretty sure we used US$ for everything (I don't remember going to get anything else...)