On the second point, the answer is that tempos are sometimes measured in beats per minute and sometimes in measures per minute. A measure can be 2, 3, 4, or 6 beats depending on the type of music. Most often 3 for waltzes and 4 for everything else.
In my personal music collection I keep track of beats per minute for all song types, just for consistency's sake and to make it easy to compare tempos of different music styles (though in some cases that's not meaningful.) But measures per minute seems to be more commonly used.