Just don't have it facing backwards down hill. You won't be able to pull it out of park. Or, at least, it'll be very difficult and make a lovely crunching noise when you do.
either cable snapped or just got really loose. probably nsapped though. Mine did that recently. The brake had frozen and no matter what I tried it wouldnt unlock so I just drove with it on. about 2 minutes later I stopped and tried it again and snap. Made my life easier and a lot less smelly.
It not thast hard to fix the ebrake cable. As long as nothing else is wrong. The first time mine went apparently 3 out of 4 brake cables severed, 2 boots got destroyed and the pads needed replacement. And that all happened while I was doing 80 on a highway.