Brake pedal pulsates when decelerating from 10mph - 0mph?

After having my brake pads changed I started to notice the ABS and Traction Control light started coming on periodically (slowing down, while turning wheel, rough road, etc.). After doing some research online, I determined that the speed sensors may either need to be replaced or rust/road grim may be causing an air gap between the wheel bearing assembly and speed sensor spacer. So, I replaced both sensors on the front tires and the lights stopped coming on, however, now I have a bigger problem I feel. When coming to a stop the brake pedal pulsates once I reach 10mph and then around 5mph it releases to the floor and I have full pedal again. If I stay under 10mph no pulsating. And to top it all off, now the ABS and Traction Control lights have randomly returned as well as the Service Brake System warning on the dash. Any help would be greatly appreciated.