85 300SD - Brakes - ABS noise/softish pedal?

[BigSkillet]

Hey, I did a search (over 500 results) and after going through 150 or so, I think I found somebody with a similar problem. But I want to ask to make sure.

The brakes seem fine as I'm making my initial stop. Then, the last 10 feet or so, when ya put a little more pressure on the pedal, it sounds like the ABS noise (during traction loss) and the pedal sinks about an inch. Not totally soft. Not all the way to the floor. Is this probably a bad master cylinder?

Side note, one morning I started the car up and had the brick brake pedal. But I made it to the end of the street to turn around, and all was good. Hasn't done that since. Did it go into self-healing mode or is that foreshadowing of a vac problem?

Thanks everybody!