[Yetti]

Ok lets start slow.

1. if you pull up on the pedal with your toe does it make any clicking noise? if so the pedal might have been held down by the brake light switch. it can and will prevent the pedal from coming to the top and letting the master cylinder refill after a brake apply.

2. if you ease the pedal down like you discribed is there a point where you feel the brakes pick up?
I suspect if the brake light switch issue doesn't fix the problem then I would put in a new master cylinder. the reason being the master applies the rear brakes first. then as it picks up load it applies the fronts. that way the systems has the default of not letting the fronts lock up first and causing an accident. I would say the master has worn out just enough to vent pressure around the seal on the apply piston under light load. if you hit it fast it applies normal because the seal is forced to stretch to meet the bore imperfections.