I don't use Repetier, but your config file looks okay. Generally, if you have a "spazzing" motor, it means one of the following is happening:
1.) Trimpots are set way too high and thermal shutdown is happening
2.) Trimpots are way too low, and the motor is stalling
3.) Acceleration, speed, or jerk is set way too high and the motor is stalling/binding
4.) Motors are wired incorrectly
Since your accel and speed values seem reasonable, and you've set the trimpots, I'd recommend trying to change motor wiring. Simplest thing to do is take the motor connector, and swap the positions of the two middle wires. Pololus have a reputation as being delicate, but they generally break only if they made a large move with the trimpots too high, had shorted pins, or were removed or had the motor unplugged while powered. Unless you did one of these to all three drivers, it's likely not the drivers' fault.
If that doesn't help, report back here, and hopefully someone more familiar with Repetier can give you further suggestions.
