One big whiff of concentrated hydrogen sulfide will kill you very dead very quickly. People tend to think they would smell it first, but if it's concentrated you'll be dead before the smell even registers.

Extremely unlikely.

Not at all.

This is a known hazard when working on waste-water networks. There are a few deaths every decade, despite nearly everyone having gas detectors (and being told to use them before going into a manhole).

At high enough concentrations, H2S just shuts down your smell receptors.

People who die in such situations don’t not smell the hydrogen sulfide. They just either have no way out quickly or they keep going in spite of the danger. I’ve been in such situations.

a contained area, like ... the cabin of a car?

The giant fire would be the much bigger problem if you are still in the car.

(The fire is smallish in a 'amount of material' sense and huge in a 'you don't want to be anything resembling close to it' sense)