Potential HCH2 Purchase, Question about normal operation

I'm looking at purchasing a used HCH, and after a few test drives I have a few questions about what is normal
1. The cruise had far more variation than I would expect. Set at 110 (km/h) i slowed on mild grades to as little as 94. Is this normal?
2. Battery charge jumped from 1/2 to full and back very quickly. Never went below 1/2. I read that jumping to empty is a recal, is this the same? Car had no assist at 1/2 charge either. I was full throttle attempting to merge, and got half of the bars of charge, and little acceleration. This was with the state of charge at 1 above half.
3. Gas gauge. This was at 3 bars when I left, after approx 30km (20 miles) it was at zero bars of fuel. On board computer said my average was 6L/100km, about 40mpg. Is this normal for the gas gauge? If so, how much is left when it is at zero bars?

If you can answer any of these for me, or direct me to a better forum it would be greatly appreciated. Also, since this is a Prius forum, I have looked at them, but there are pretty much zero for sale in my area at any time.
Thanks