What is the REAL Ah rating and/or Wh rating? I.e., printed on the battery: 20v 5Ah 100Wh. Since it runs at 18v, it is either 5Ah OR 100Wh, not both.

The numbers which you quote (the numbers written on the battery) are rounded for the sake of simplicity. First, this battery has max voltage of around 20 volts (when fully charged and without the load). Its voltage changes as it discharges, it may change depending on the power drawn from the battery, and can even drop below 18 volts. Neither 5 AH nor 100 WH is correct because these are theoretical parameters for a certain discharge rate and a certain end state (you probably will not run your battery to a complete discharge, in real life). Both numbers are a ballpark estimate for the capacity, some kind of a guidance. You are right, at 5 AH at 18 volts does not add up to 100 WH. It add up to 90 WH. Oh well, a lot of marking is going on here. I suspect, 90 WH would be more correct, but why would the manufacturer state a lower number?

Do these have the fule gage led lights system?

Yes they do.Heavier than the smaller batteries.Good for the high draw tools but even with these,something like a sawzall will run them down in 20 minutes.

Can a frozen li-ion battery be charged? can a li-ion battery be charged if it is warm or hot?

I have charged these batteries in freezing weather 25-32 degrees as well as today when it was 105. Keep them out of the sun while charging in summer or they will get too hot and fail to charge correctly.