I have about 30 scenes and the speaking level varies greatly. Is there a way to select all the scenes' audio and make it so they're all at more-or-less the same level?
Sorry I'm not much of an audio tech, but I don't think there is anything in MEP to auto adjust clips to the same level. After all, what if you do have genuinely quiet clips and very loud ones in you mix? Only suggestion is to try 'Normalize' from the right click menu over your audio objects. If it's not right just undo.
For manual adjustment select 'Volume curve' from the same menu and you can create and drag points to vary the volume between and within individual objects.