battery box shouldn't make any difference with levels, but be sure to use it and make sure the battery is fresh (replace every 3 months or so, and don't leave mics plugged into it when you are not recording or getting ready to record, that is don't leave it on the shelf for days with the mics plugged into the battery box)
you absolutely need the battery box when recording!
you can record at a lower level than red, I try to keep the db meters at -12 or less, but record at 24 bit then you can amplify when you are processing your recording.