Master light+vsc+yellow ((!))+intermittent check engine light+"Stalling" symptoms

I have a 2005 Prius with almost 219000 (!) on it. It runs great, but about three months ago the check engine light started coming on and turning off by itself. I had a scan done on it and they mentioned possibly a bad O2 sensor. Friday, I was on the highway and the master light (big red triangle with ! in it), the VSC, and the yellow ((!)) brake light came on. I pulled over, shut the car off and turned it back on. The master light and check engine light was still on. The VSC and yellow ((!)) light came back on a few miles down the road. I pulled off the highway and took it to a mechanic who scanned it again and said that there were several codes that came up including a large exhaust leak.The car was running fien and I had to go to work on Saturday overnight, so I drove the car. Other than the lights, nothing seemed wrong. However, the lights would turn on and off intermittently and I was getting horrible mpg (8-12 mpg on local roads). On the way home, the car seemed to stall (clearly not a manual though). The power steering cut out and a message syaing something like transmission parking brake malfunction ( I couldn't read it all because it went away). I was only about .1 miles from home, so I shut the car off and turned it back on. Not another 50 feet and the car "stalled" again. This time, I couldn't get it to turn off or anything. I left it running and unlocked (though I took the key with me) and waled home to use a phone. I called AAA and went back to the car. I put the key fob in the keyhole and tried shutting the car off again. This time, it shut off so I turned it back on and slowly drove it home. Any thoughts?

 

could this be a restricted cat converter due to a bad o2 sensor?