Q: Drive belts make high-pitched chirping sound

Firstly, I would recommend replacing your serpentine belt as it is a regular maintenance item on all vehicles with internal combustion engines that use a belt. The reason for the noise is that over time after the belt has been in use for a while it starts to stretch out. This causes the belt to be looser across the pulleys and sometimes it will slip. This slip is what you are hearing.

As for the brake pulsation, that is almost certainly an issue with your brake rotors - particularly your rotors in the front. If your brake rotors have any runout or warpage, you will be able to feel this in the brake pedal when applying the brakes. When this happens you usually have two options. I would replace the brake pads and replace the brake rotors together. Once the rotors have a smooth surface, the brake pulsation will go away. Ensure that this work is performed by a certified technician to ensure that the job is done correctly and your car will run safely.