There is nothing to discuss as to what the problem is, and this is where you need to sart: a complete hydralic system rebuild. The booster and lines may be okay, but the master cylinder and wheel cylinders need to be replaced. You will experaince a catostrophic brake failure if you continue to drive the car.

Master cylinder and wheel cylinders are somewhere in the $150 raneg, with some possible change leftover. Rust in the drums can be knocked out with coarse sandpaper and the crud can be buffed off the shoes. I installed new shoes even though they still showed 80% because I couldn't see putting old shoes back on. (By the way, it sounds as if the booster has failed, so that might be on the list too. But you can still stop the car with a faulty booster. It 'dont work that way with hydralic failure.)

Forget collision damage costs, or worse, have you priced what it cost to repair a paint chip? You'll find a brake overhaul one of the cheapest things you can to for the car, and it's the very first thing that needs to be done. Cardinal rule #1: The car must stop.