You are the same height as me, but are 60 lbs lighter. I think you may be adding a light day a bit prematurely. If I were you, I would continue doing the program, especially focusing on eating correctly, before you start adding all these complicated things in.
As for the breathing, it's not cheating to take a few breaths, but for a set of 5, it is probably not necessary to wait longer than a few seconds between reps.