I would contact your SP friend and inform him of the phone call. Document everything and ask him for copies of any reports he makes out. If you have to, get a restraining order.
I would definitely talk to your police buddy and ask him about getting a CCW and training with whatever you buy. I would personally recommend a Glock .40, they are reliable, comfortable and they will stop someone with one shot. You might want to ask your boss if he can have someone else in the store with you at opening or closing, so you aren't as vulnerable.