1993 Cadillac Deville brakes making me think about killing

My mom called me stranded saying that the brakes had gone out. Pedal went all the way to floor and was making "squishy sound". I went to help and because we were in a crackhead neighborhood I would not leave her garaged 93 deville to be plundered. Or traded for a rock. Against her concern for my safety, I decided to try and drive it anywhere else but there after stopping a few times with the strength of five men against the pedal. Traffic was slow enough for me to make it all the way home. I knew it was the brake booster from past experience, and could hear the boost of air escaping from the diaphragm in booster. Removing booster revealed a tear in it and I knew what I had to do to fix. This is when the insanity began. After replacing booster, without removing master cylinder from brake lines, when I started vehicle the brake pedal drops almost to floor engaging brakes automatically. When I cut the car off it returns to normal position. Please help me stay out of jail, or from blowing up a really nice cadillac. Pending