Set your EPA's to 5%.
Should have little or no movement to the servos when you apply steering or throttle. Then increase your steering Left/Right EPA until you reach max throw and hear the servo buzz because it's pushing against the steering smashed at full lock. Then dial it back a little so the steering can go to full throw without the servo pushing hard.
Same for throttle. Increase your EPA while holding throttle until the barrel fully opens. Just barely fully open, maybe even leave a little showing. Then make sure that the linkage can still travel another 1/8th inch without the servos help to account for chassis flex.
Adjust your brake EPA until your servo rocks a little on it's rubbeer mounts, no more. Pulling extra hard on the brakes won't stop you faster. Use as littlle brake as possible. Make sure rotors and calipers are in good shape and free of excess play.
Your open EPA settings killed your servos. Try Hitec 7955's once you get a handle on setting EPA's. When servos get "jumpy" they're about to die. It takes some experience to be able to quickly see the difference between radio glitching and servo jumping. Todays better radios shouldn't glithc at all though.