95' T-Bird braking issues.

Here are the problems so far with the car.

When I got it the brake pedal was very hard to push down and the car had problems braking. There was no sound of grinding or anything that would lead me to believe it was the pads or any of that. When I checked the brake fluid it was, well, gross. So I bled the two rear brakes which actually alleviated the pressure on the brake pedal when we finished the passenger rear system. It was strange, it went from a very hard to push down brake pedal to light brake pedal. After that I still had to push the brake pedal to the floor in order to get the car to stop, and even then had to throw the car in park to get it to stop completely. We also noticed that even when the braking was hard, there was an air leak sound coming every time I pulled up on the brakes, only when the car was moving or shortly after parking. This led me to believe there was something wrong with the power brake booster or something connected to it. That’s where I’m at a loss, I don’t know what to do next in diagnosing what might actually be the problem.

I don't want to just replace the power booster without finding out if that's the problem. I figured it had to be since the brake pedal was very stiff, though after bleeding the rear brakes it went to the very opposite, but there was still the sound of an excessive amount of air leaking.

Welcome to the forum DeadEyeMouse. Check the vacuum one way valve that is on the booster. Remove it and you should be able to suck air through it from the side that the vacuum hose is on but you shouldn't be able to suck air through the side that pushes into the vacuum booster. Check the vacuum hose to be sure it isn't cracked/split and leaking. Do you see any brake fluid around the area that the booster connects to the master cylinder? That would mean the master cylinder is leaking into the booster which can ruin the diaphram. If the one way valve checks out then put everything back together. Before starting the car, depress the brake pedal and hold it there. Start the car and the pedal should depress another 1/4" or so. If it doesn't move, replace the booster. When you bleed the brakes you should start at the passenger side rear, then the driver's side rear, then the passenger side front and finally the driver's side front. Be sure to bleed all four locations, not just the rear. Wait for clear fluid to come out of all four bleeder screws