yes, it's M
i have 1 S, too, and it's a perfect size for daily use

not silly at all, i get asked the same question pretty much every time i meet a new person

no, i don't take them off, they all are sterling silver and i am not scared to get them wet, etc
i take them off only when travel by air from Europe back here, because when i am flying out i just go straight to the personal check-up booth and they scan me with the metal detector quickly and i pass. In Europe they are not as flexible and once it took me good 15 minutes to take them ALL off in CDG Airport in France

now i prepare before i go through the security control