Both those faults should be easy to do some checks on. Battery voltage is easy enough to check. If it is low, it is possibly a fault with the dc-dc converter. You might not be aware, but the hybrid doesn't have an alternator in the conventional sense, the power for the 12V system ultimately comes from hybrid battery and is lowered to 13.9V to charge/power the 12V systems. I would expect there to be other tell take signs of low voltage such as locks not working, stereo not working, lights not working, etc.
The open circuit in the stop light switch could be a red herring due to low voltage, but the switch is easily checked.
If you have Toyota techstream it will give access to far more information.
It might be something as simple as a duff 12V battery, of course, or a loose battery terminal. Hopefully it is something simple.