I’ve actually replaced these in two houses, and yes, they’re dangerous, but honestly a little common sense and a straightforward (printed, with a buddy double-checking) list of steps you take with each quarter turn.
It’s super important to have the right torsion bars. Don’t try to invent your own.
On the one hand, nothing went wrong because I was careful. And rebar actually works really well.
On the other hand, it was pretty dicey, especially near the maximally-wound state when you're putting serious muscle into another quarter turn.
110% agreed on it being a 2 person job though. Reason #1: so someone is there to call 911. Reason #2: you'll need someone to cable up the drums while you're adjusting the spring, and it's way easier with 2 pairs of hands.
The replacement spring was constructed differently, with the "hook" portion replaced by two complete loops of metal. The safety cable runs through that and would hold it back during a similar failure.