seems like you are not getting any assist from the booster.

I would verify it even does anything for the pedal first.
start the car press the brake pedal. see how easy it is and how far down it goes.
I would let it idle for a bit and try and see if it changes at all. Say 5 min or so depending on the vacuum that engine generates.

then shut off the car and pump the brakes 3 or 4 times. by the 5th it should be out of any stored vacuum.
see if it is any different.

if it isn't any different, or it is minor, I would then be checking the booster again. See if something was assmebled wrong.