I'm guessing if the ISS was no longer able to sustain life support, Starliner would be used. Guaranteed loss of life by staying on ISS or having an unknown <100% chance of surviving using Starliner, of course it will be chanced.

I'm not really sure what point your question is attempting to get at

They don't have a way to come back to Earth right now on a Spaceship cleared for human flight.

I'm sure the astronauts would much prefer to have a Dragon available, but I don't think NASA's "cleared for human flight" means much. After all, 4% (14/355) of all the astronauts that flew on the space shuttle died when their vehicles exploded.

Starliner is the evacuation option right now. It's a risky one, but until Crew-8 is reconfigured their only option.

ISS is huge, and is very unlikely to fail all at once. In a case of a catastrophic failure, they could stay in a less affected part of the station. All life-critical systems on spacecraft are duplicated and triplicated. With the current SpaceX launch capabilities, a rescue Crew Dragon could arrive within days if not hours.

The evacuation option right now is Starliner

They would use Starliner, which was announced a few weeks ago.