1) do you have an example... most likely you have to update the width somewhere else on the page that may not have been updated properly.
2) It will show only the US if you only enter US addresses... so filter the database... maybe I misunderstood... what is happening now? Often a url example goes a long way in allowing for precise responses to questions.
3) You could add code to do this... either update the line in the existing map include: map.setCenter(new GLatLng(37.4419, -122.1419), 13);
or add your own reference on the page:
wagmp_map_1_obj.setCenter(new GLatLng(37.4419, -122.1419), 13);
Look up more about the .setCenter() method of the map object at google.com
4) We will be updating pro maps to allow for more data points to be plotted very soon. Currently the restriction is based on the api restricitons of Google that allow a certain number of geocode requests per second, minute, hour, etc... so ironically you can sometimes show more points on a slower server.