I keep my opinion, that the circuit behaviour can be understood from the datasheet description, also with the Fairchildsemi
drivers, although I mainly refered to IRF. To understand the basic operation, assume the driver transistors as ideal switches (possibly
with a finite rDSon). The bootstrap power supply is extern to the chip (diode and capacitor), except for an internal zener diode intended
to protect the chip rather than the connected FET. You'll easily see, that the driver output voltage can't be basically higher than the external
supply, which is typically between 12 and 15 V.
Now addressing some details aspects.
What do VB and VS typically look like? Are they both swinging up and down, following the load voltage? To me, the data sheets are not clear, as shown in the attached figures. What are the HO and LO voltages, and how do I know if they are within the gate voltage ratings?
Part of the question seems ignorant to me, e.g. if VS is swinging with the load voltage. It's connected to the load by a wire.
Do you see a way how it's not swinging with the load voltage?
The other points can be answered by following the above considerations. As said VS isn't actually a question, VB is kept at a constant
difference to Vs (at least in a short time scale) by the bootstrap cap. HO and LO can swing between zero and the respective supply.
Can I assume the 7382 would work at 50 kHz, 50% duty cycle?
Surely.
A special point is about Vs allowed to swing below GND. That't not basic operation, but often required by the non-ideal behaviour of
the connected power stage.