All of the brake hoses have been replaced with new hoses (four front, two rear), so collapsed hoses are not the issue.

I had the same experience using each method that I tried (pressure bleeding, vacuum bleeding, then having a friend pump the brakes while alternately opening and closing the bleed screw) -- a bit of old fluid would come out (not much), followed by lots of nothing. Kept 15 lbs of pressure on the pressure bleeder, which has always been more than enough to bleed the brakes on every other car I've worked on.

I have no idea whether the MC is good or not. Ordinarily, I'd open up the vacuum booster to see if fluid was leaking into it from the MC. The funny thing is that the fluid level in the MC reservoir was not dropping much, if at all, during my attempts to vacuum bleed and to use the traditional pedal pump method.