Brakes acting up BUT no codes!!!!

Okay people, I have searched the forums all morning and got some great info but I need more.
1996 Trans Am, LT1 motor, 4 wheel disc, Auto....

Brake pedal usually goes about half way down to slow and stop the car, kindy soft, but works good....

Couple days ago....brake pedal got hard as a rock when trying to stop the car, and as it is slowing down it was kinda pulsing, like the ABS was working, locking the wheels then unlocking them!!! the Low trac light comes on as well when this happens....today it is doing just about every time I drive the car. Went to Auto Zone, no codes came up on the car, so does that elimate the sensors and such? I checked the line from the booster to the intake, looked good, I did notice just a tad of fluid that had leaked out between the master and the booster, looked old though, not recent....do you think the seals are gone in the booster, or the check valve, which is located where?

I am just hoping the sensors are okay, I dont mind changing out a booster, so give me some suggestions of other things that I might need to check on this, kinda getting scared to drive it!!!!

thanks in advance!!!!

sounds like a booster or master cylinder but dont know why the low track light comes on try a pont dealer it will be like 50 bucks but they have a better scanner and more knowledg than some clow at az