No, they have no internal 5 digit precision - or in fact they have, but the remaining digits are normally zero. The values internally used by the broker API are really the same as displayed in the FXCM platform, with no hidden digits.

The values do indeed fluctuate. FXCM changes them from time to time and adapts them to the exchange rate. When you look into the file "AssetsMini.dat" in your History folder, which is for simulating a mini lot account, you can see that the value was 0.78 in 2012. So in this way you're right that the simulation does not reflect the current situation. But you can update that file anytime to your current account parameters with the procedure described under "Data Import".