Easy question first. The three OSTs are due to your having three addresses being read by Outlook: most likely.
I would start by going through all of these PST files.
Remember, you can open a PST anywhere in your computer from the file menu.
Ok. This is what I would do to solve your problem. You may note that I am being too cautious, but I have been confused by multiple PSTs too many friggin' times. I play it slow and safe and clear.