Will answer each of these questions separately (ideally each different question should be in its own topic):
PsychoPy will automatically store the reaction time in seconds but if it is important to you, you could add another variable that is converted to milliseconds. e.g. insert a code component, and in its “End routine” tab, put something like this:
thisExp.addData('RT_in_ms', key_respB3.rt * 1000)