car not shuting down

my 79 300d euro has two problems, not sure if they are related. 1st it is not turning off. 2nd the brakes are acting odd. sometimes the pedal is rock hard, sometimes it is so soft it goes to the floor with almost no braking power. to make this a little more complicated,the longer you drive the tighter the brakes get. after a 30 min. trip simply pushing in the clutch causes the car to slow rapidly! when to shut the engine off you car hear the brakes releasing pressure. do you think it is the brake booster or vacuum pump or both?