Brake Electric Antilock problems of the 1996 Mazda 626

While applying normal pressure on (abs) brakes, brake pedal would drop completely to floor, finally would engage enough to stop; happens intermittenly; took to dealer, he could not find or fix problem.

Driving vehicle, when applying brakes vehicle would fishtail for no reason; would also make groaning noise; happens at various speeds. A lot of vibrations would occur in the steering column at same time; took to dealer & mechanic could not find problem; went through autocap in order for a rep. To check vehicle.

When brakes are depressed there is extended stopping distance. Please provide further information.