Help diagnosing anti-lock brake condition

Please advise if this would not be best forum for this question?

1995 V6, 150,000, auto anti-lock brakes, original owner.

The brakes on this Mustang behave differently than two other Fords I have driven.

One was a Ford station wagon in the 70's, the other was some larger rental in 1986 (not as big as a Crown Vic).

Both of those cars had power brakes, where if you pressed the brake pedal a little too hard, the brakes were so strong the front end of the car nose dived. You actually had to press very gently for normal braking.

Had a 70 Cadillac like that too.

I had a rich friend in high school who used to play with his Lincoln Continental by bouncing the front end three or four feet up and down by applying the brakes when approaching a stop light.

Others cars, except for the 1970 Cadillac, I have driven were not this way. The car seemed to brake in proportion to the pedal pressure, and in an emergency stop would cause all four wheels to skid.

A Mustang rental driven before purchase of this car did not have such touchy brakes as the other two Fords from years ago.
(not sure if the rental had anti-lock brakes.)

This Mustang has power anti-lock brakes, and the pedal was never anywhere as near as sensitive, but in a panic stop would make a noise like a grinding noise (grishhh) (noise was not from worn pads) and the car would stop in a real hurry. Except in the rain when this noise would repeat over and over and the car would require much a much longer distance to stop.

They say anti-lock brakes activate several times per second to emulate a driver pumping the brakes, and release just before the tire skids. I have had at least two occasions where I was able to stop just short of a collision where the brakes made a super grishhh noise, and if the tires would have skidded I would have slammed into the other car.

About a month ago the brakes behaved differently in that no matter how much pressure was put on the pedal the car seemed to brake at the same pace, much slower than before, and seemingly at about the same rate throughout the entire stopping distance.

Seemed like before if during a stop, other than a panic stop, if you pressed the pedal harder near the end of the stop the brakes would work harder and stop the car faster. If you pressed hard enough on the tail end of the stop the grishhh noise would occur and the car would stop in a real hurry.

Had both front and rear rotors resurfaced, new pads.

Now after 400 miles on highway (time to break in new pads if required?) the brakes seem to stop the car at about the same rate all through the stop, like a month ago, and in a panic stop will not make the grishhh noise.

Now within a couple of car lengths of a complete stop from 60 mph those last few car lengths seem to take forever and no matter how hard the pedal would be pressed at that point the car will just continue to stop at the same pace.

All brake parts are original except for the front rotors (replaced twice due to warping; front wheel shake)

I was told 18 months or so ago this car has a low vacuum reading, but the car drives the same as always.

Any similar experience, or opinions on what might be causing this change in braking ability on a high mileage car?

Not sure which brand pads were installed (cost about $45 a set), but this problem started a month before these new pads were installed. Previous front pads were $90 because they were supposed to be heat build-up resistant. Rotors warper in same distance as always.

Brakes are the vast majority of the time used as gently as possible.

Perhaps reduced power booster assistance? I have heard of a vacuum can, but would have to research how to install one.

No warning lights, pedal not mushy, pedal seems to stop as same place as before pad replacement.