The recommended dosage for hairloss is 1mg, which is exact dosage of propecia. So you could cut the proscar pills into 5 pieces. If you experience side effects, you could try lowering the dosage. It's been found that .2mg is almost as effective as 1mg in maintaining/growing hair.
The question about storage is a great one. I have been storing my proscar in the refrigerator, in an attempt to extend longevity. I imagine as long as it's kept dry in its original package, and not allowed to freeze, it should be fine. Although, I just performed a search, and one site states, "Store at room temperature between 59 and 86 degrees F (15-30 degrees C) away from light and moisture."
Anyone have a more definitive answer as to why refrigeration might not be a good idea?