1996 Cadillac Deville Sudden and Recent Issues

I have a 96 Cadillac Deville with 133,000 miles on it. I've had it about a year and haven't experienced any issues until about 2 weeks ago. I was driving home and all of a sudden the car just shut off. I checked the oil, and found that it was so low that it was basically gone so I went and put 5 quarts in, which astonished me because I wasn't due for an oil change for another 1000 miles. Since then the car has been fine, except that it rocks a bit when I turn right to park in my driveway. This morning, however, I got a "service brake fluid switch" message and the brake light came on. The brake light flickered on and off over the duration of my trip, which was only about 10 minutes. Can anybody give me any insight as to what is going on with my car? I'm worried that things are starting to fall apart because I can't afford to service it and it's the only vehicle I have.

Thank you!