At the risk of sounding old and mechanically conservative .... which I do happen to be...
You need to stop putting yourself and others at risk until you resolve the brake issue.
On that old a car ... and given the relative importance of brakes... I suggest you put a new master cylinder and a new brake booster on your car. They will last a long time and serve you well while you fix the other quirks in your car...
You need to check for air in your brake lines. In addition to those other items which can cause changing symptoms air in the lines can also ....and if they are all squeegy they can really mess up your diagnostic flow.
Seriously, it is an old car and multiple things can be wrong at the same time...