I would be inclined to think of a bad booster if you can stall the engine by pumping the brakes, it shouldn't use that much vac. Check the line (probably separate).

The broken fitting won't help, but wouldn't cause your problem.

You need to bleed the brakes and check the brake line hoses, it's possible one is bad.

Lack of vac at the booster makes the pedal hard, not sink, so I also would consider the fact that the "new' master may be bad, it acts just like a bad master cylinder!.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!